diff --git a/web/app/math/qr.js b/web/app/math/qr.js
index cd940f29..458f7edd 100644
--- a/web/app/math/qr.js
+++ b/web/app/math/qr.js
@@ -18,7 +18,7 @@ TCAD.math.QR = function(matrix) {
   var vec = TCAD.math.vec;
   this.matrix = matrix;
   var nR = this.matrix.length;
-  var nC = this.matrix[0].length;
+  var nC = nR == 0 ? 0 : this.matrix[0].length;
 
   this.qrRankingThreshold = 1e-30; //??
   this.solvedCols  = Math.min(nR, nC);
diff --git a/web/app/math/vector.js b/web/app/math/vector.js
index 951bf317..5c98dda9 100644
--- a/web/app/math/vector.js
+++ b/web/app/math/vector.js
@@ -50,10 +50,31 @@ TCAD.Vector.prototype.minus = function(vector) {
   return new TCAD.Vector(this.x - vector.x, this.y - vector.y, this.z - vector.z);
 };
 
+TCAD.Vector.prototype._minus = function(vector) {
+  this.x -= vector.x;
+  this.y -= vector.y;
+  this.z -= vector.z;
+  return this;
+};
+
+TCAD.Vector.prototype._minusXYZ = function(x, y, z) {
+  this.x -= x;
+  this.y -= y;
+  this.z -= z;
+  return this;
+};
+
 TCAD.Vector.prototype.plus = function(vector) {
   return new TCAD.Vector(this.x + vector.x, this.y + vector.y, this.z + vector.z);
 };
 
+TCAD.Vector.prototype._plus = function(vector) {
+  this.x += vector.x;
+  this.y += vector.y;
+  this.z += vector.z;
+  return this;
+};
+
 TCAD.Vector.prototype.normalize = function() {
   var mag = this.length();
   if (mag == 0.0) {
diff --git a/web/app/sketcher/constr/solver.js b/web/app/sketcher/constr/solver.js
index e974deff..2f22a7ad 100644
--- a/web/app/sketcher/constr/solver.js
+++ b/web/app/sketcher/constr/solver.js
@@ -206,6 +206,12 @@ TCAD.parametric.lock2Equals2 = function(constrs, locked) {
 };
 
 TCAD.parametric.diagnose = function(sys) {
+  if (sys.constraints.length == 0 || sys.params.length == 0) {
+    return {
+      conflict : false,
+      dof : 0
+    }
+  }
   var jacobian = sys.makeJacobian();
   var qr = new TCAD.math.QR(jacobian);
   return {
@@ -231,13 +237,18 @@ TCAD.parametric.prepare = function(constrs, locked, aux, alg) {
     sys.setParams(point);
     return sys.makeJacobian();
   };
+  var nullResult = {
+    evalCount : 0,
+    error : 0,
+    returnCode : 1
+  };
   
   function solve(rough, alg) {
-    if (constrs.length == 0) return;
-    if (sys.params.length == 0) return;
+    if (constrs.length == 0) return nullResult;
+    if (sys.params.length == 0) return nullResult;
     if (TCAD.parametric.diagnose(sys).conflict) {
       console.log("Conflicting or redundant constraints. Please fix your system.");
-      return;
+      return nullResult;
     }
     
     switch (alg) {
diff --git a/web/app/sketcher/fetchers.js b/web/app/sketcher/fetchers.js
index ae60da45..969ada54 100644
--- a/web/app/sketcher/fetchers.js
+++ b/web/app/sketcher/fetchers.js
@@ -102,3 +102,24 @@ TCAD.TWO.ParametricManager.prototype._fetchTwoLines = function(objs) {
   }
   return lines;
 };
+
+TCAD.TWO.utils._fetchSketchObjects = function(objs, silent, matching) {
+  var fetched = [];
+  for (var i = 0; i < objs.length; ++i) {
+    for (var j = 0; j < matching.length; j++) {
+      if (objs[i]._class ==  matching[j]) {
+        fetched[j] = objs[i]; 
+        matching[j] = null;
+      }
+    }
+  }
+  if (fetched.length != matching.length) {
+    if (silent) {
+      return null;
+    } else {
+      throw "Illegal Argument. " + matching + " required";
+    }
+  }
+  return fetched;
+};
+
diff --git a/web/app/sketcher/helpers.js b/web/app/sketcher/helpers.js
new file mode 100644
index 00000000..255d0bb6
--- /dev/null
+++ b/web/app/sketcher/helpers.js
@@ -0,0 +1,123 @@
+
+
+TCAD.TWO.FilletTool = function(viewer) {
+  this.viewer = viewer;
+};
+
+TCAD.TWO.FilletTool.prototype.makeFillet = function(point1, point2) {
+  function shrink(point1) {
+    point1.parent.a;
+    if (point1.id === point1.parent.a.id) {
+      var a = point1.parent.b;
+      var b = point1.parent.a;
+    } else {
+      var a = point1.parent.a;
+      var b = point1.parent.b;
+    }
+    var d = TCAD.math.distanceAB(a, b);
+    k = 4 / 5;
+    b.x = a.x + (b.x - a.x) * k; 
+    b.y = a.y + (b.y - a.y) * k;
+    return new TCAD.Vector(a.x - b.x, a.y - b.y, 0);
+  }
+  
+  var v1 = shrink(point1);
+  var v2 = shrink(point2);
+  
+  if (v1.cross(v2).z > 0) {
+    var _ = point1;
+    point1 = point2;
+    point2 = _;
+  }
+  
+  var vec = new TCAD.Vector();
+  vec.setV(point2);
+  vec._minus(point1);
+  vec._multiply(0.5);
+  vec._plus(point1);
+  
+  var arc = new TCAD.TWO.Arc(
+      new TCAD.TWO.EndPoint(point1.x, point1.y), 
+      new TCAD.TWO.EndPoint(point2.x, point2.y), 
+      new TCAD.TWO.EndPoint(vec.x, vec.y))
+  point1.parent.layer.objects.push(arc);
+  var pm = this.viewer.parametricManager;
+  arc.stabilize(this.viewer);
+  pm._add(new TCAD.TWO.Constraints.Tangent( arc, point1.parent));
+  pm._add(new TCAD.TWO.Constraints.Tangent( arc, point2.parent));
+  pm._add(new TCAD.TWO.Constraints.Coincident( arc.a, point1));
+  pm._add(new TCAD.TWO.Constraints.Coincident( arc.b, point2));
+  
+  var solver = pm.solveWithLock([]);
+//  var solver = pm.solveWithLock([point1._x, point1._y, point2._x, point2._y]);
+  pm.notify();
+  this.viewer.refresh();
+};
+
+TCAD.TWO.FilletTool.prototype.mouseup = function(e) {
+  var candi = this.getCandidate(e);
+  if (candi == null) return;
+  var point1 = candi[0];
+  var point2 = candi[1];
+  
+  var pm = this.viewer.parametricManager;
+  for (var i = 0; i < pm.subSystems.length; i++) {
+    var subSys = pm.subSystems[i];
+    for (var j = 0; j < subSys.constraints.length; j++) {
+      var c = subSys.constraints[j];
+      if (c.NAME === 'coi' && 
+          ((c.a.id === point1.id && c.b.id === point2.id) ||
+           (c.b.id === point1.id && c.a.id === point2.id)))   {
+        pm.remove(c);
+        this.makeFillet(point1, point2);
+        this.viewer.deselectAll();
+        return;
+      }
+    }        
+  }
+};
+
+TCAD.TWO.FilletTool.prototype.getCandidate = function(e) {
+  var picked = this.viewer.pick(e);
+  if (picked.length > 0) {
+    function isLine(line) {
+      return line != null && line._class === 'TCAD.TWO.Segment';
+    }
+    var res = TCAD.TWO.utils._fetchSketchObjects(picked, true, ['TCAD.TWO.EndPoint']);
+    if (res == null) return null;
+    var point1 = res[0];
+    if (!isLine(point1.parent)) return;
+    var line2 = null;
+    for (var i = 0; i < point1.linked.length; i++) {
+      var point2 = point1.linked[i];
+      if (isLine(point2.parent)) {
+        return [point1, point2];
+      }
+    }
+  }
+  return null;
+};
+
+TCAD.TWO.FilletTool.prototype.keydown = function(e) {};
+TCAD.TWO.FilletTool.prototype.keypress = function(e) {};
+TCAD.TWO.FilletTool.prototype.keyup = function(e) {};
+TCAD.TWO.FilletTool.prototype.cleanup = function(e) {};
+
+TCAD.TWO.FilletTool.prototype.mousemove = function(e) {
+  var needRefresh = false;
+  if (this.viewer.selected.length != 0) {
+    this.viewer.deselectAll();
+    needRefresh = true;
+  }
+  var candi = this.getCandidate(e);
+  if (candi != null) {
+    this.viewer.mark(candi[0], TCAD.TWO.Styles.SNAP);
+    needRefresh = true;
+  }
+  if (needRefresh) {
+    this.viewer.refresh();
+  }
+};
+TCAD.TWO.FilletTool.prototype.mousedown = function(e) {};
+TCAD.TWO.FilletTool.prototype.mousewheel = function(e) {};
+
diff --git a/web/app/sketcher/main2d.js b/web/app/sketcher/main2d.js
index 6b37d97f..7155f805 100644
--- a/web/app/sketcher/main2d.js
+++ b/web/app/sketcher/main2d.js
@@ -41,6 +41,10 @@ TCAD.App2D = function() {
   this.registerAction('pan', "Pan", function () {
     app.viewer.toolManager.releaseControl();
   });
+  
+  this.registerAction('addFillet', "Add Fillet", function () {
+    app.viewer.toolManager.takeControl(new TCAD.TWO.FilletTool(app.viewer));
+  });
 
   this.registerAction('addDim', "Add Dimension", function () {
     app.viewer.toolManager.takeControl(new TCAD.TWO.AddDimTool(app.viewer, app.viewer.dimLayer, function(a,b) {return new TCAD.TWO.Dimension(a,b)} ));
diff --git a/web/app/sketcher/parametric.js b/web/app/sketcher/parametric.js
index 805e6073..a57269e9 100644
--- a/web/app/sketcher/parametric.js
+++ b/web/app/sketcher/parametric.js
@@ -298,6 +298,12 @@ TCAD.TWO.ParametricManager.prototype.solve = function() {
   solver.sync();
 };
 
+TCAD.TWO.ParametricManager.prototype.solveWithLock = function(lock) {
+  var solver = this.prepare(lock);
+  solver.solve(false);
+  solver.sync();
+};
+
 TCAD.TWO.ParametricManager.prototype.prepare = function(locked) {
   return this._prepare(locked, this.subSystems);
 };
@@ -313,11 +319,12 @@ TCAD.TWO.ParametricManager.prototype._prepare = function(locked, subSystems) {
     solve : function(rough) {
       for (var i = 0; i < solvers.length; i++) {
         var alg = subSystems[i].alg;
-        if (solvers[i].solve(rough, alg) !== 1) {
-          //alg = alg == 1 ? 2 : 1;
-          //if (solvers[i].solve(rough, alg) == 1) {
-          //  subSystems[i].alg = alg;
-          //}
+        var res = solvers[i].solve(rough, alg);
+        if (res.returnCode !== 1) {
+          alg = alg == 1 ? 2 : 1;
+          if (solvers[i].solve(rough, alg).returnCode == 1) {
+            subSystems[i].alg = alg;
+          }
         }
       }
     },
@@ -351,6 +358,11 @@ TCAD.TWO.ParametricManager.prototype.prepareForSubSystem = function(locked, subS
     return Math.abs(p1.get() - p2.get()) <= 0.000001
   }
   var system = this.__getSolveData(subSystem, []);
+  system.sort(function(a, b){
+    a = a[0] === 'equal' ? 1 : 2;
+    b = b[0] === 'equal' ? 1 : 2;
+    return a - b;
+  });
   var tuples = [];
   for (i = 0; i < system.length; ++i) {
     var c = system[i];
diff --git a/web/sketcher.html b/web/sketcher.html
index 8ad07b43..e348a889 100644
--- a/web/sketcher.html
+++ b/web/sketcher.html
@@ -189,6 +189,7 @@
   <script src="app/sketcher/shapes/circle.js"></script>
   <script src="app/sketcher/shapes/segment.js"></script>
   <script src="app/sketcher/shapes/dim.js"></script>
+  <script src="app/sketcher/helpers.js"></script>
 
   <script src="app/math/vector.js"></script>
   <script src="app/math/math.js"></script>
@@ -274,6 +275,7 @@
     --><button class="btn tbtn act-addMultiSegment" style="background-image: url(img/mline.png);" type="submit" value=""></button><!--
     --><button class="btn tbtn act-addCircle" style="background-image: url(img/circle.png);" type="submit" value=""></button><!--
     --><button class="btn tbtn act-addArc sep" style="background-image: url(img/arc.png);" type="submit" value=""></button><!--
+    --><button class="btn tbtn act-addFillet sep" type="submit" value="">F</button><!--
     --><button class="btn tbtn act-addHDim" style="background-image: url(img/hdim.png);" type="submit" value=""></button><!--
     --><button class="btn tbtn act-addVDim" style="background-image: url(img/vdim.png);" type="submit" value=""></button><!--
     --><button class="btn tbtn act-addDim" style="background-image: url(img/dim.png);" type="submit" value=""></button><!--