diff --git a/ladybug_geometry/geometry3d/line.py b/ladybug_geometry/geometry3d/line.py
index 46860074..63c6f9b9 100644
--- a/ladybug_geometry/geometry3d/line.py
+++ b/ladybug_geometry/geometry3d/line.py
@@ -3,6 +3,7 @@
 from __future__ import division
 
 from .pointvector import Point3D, Vector3D
+from ..intersection3d import closest_point3d_on_line3d_infinite
 from ._1d import Base1DIn3D
 
 
@@ -123,6 +124,32 @@ def is_vertical(self, tolerance):
         """
         return abs(self.v.x) <= tolerance and abs(self.v.y) <= tolerance
 
+    def is_colinear(self, line_ray, tolerance, angle_tolerance=None):
+        """Test whether this object is colinear to another LineSegment3D or Ray3D.
+
+        Args:
+            line_ray: Another LineSegment3D or Ray3D for which co-linearity
+                with this object will be tested.
+            tolerance: The maximum distance between the line_ray and the infinite
+                extension of this object for them to be considered colinear.
+            angle_tolerance: The max angle in radians that the direction between
+                this object and another can vary for them to be considered
+                parallel. If None, the angle tolerance will not be used to
+                evaluate co-linearity and the lines will only be considered
+                colinear if the endpoints of one line are within the tolerance
+                distance of the other line. (Default: None).
+        """
+        if angle_tolerance is not None and \
+                not self.is_parallel(line_ray, angle_tolerance):
+            return False
+        _close_pt = closest_point3d_on_line3d_infinite(self.p1, line_ray)
+        if self.p1.distance_to_point(_close_pt) >= tolerance:
+            return False
+        _close_pt = closest_point3d_on_line3d_infinite(self.p2, line_ray)
+        if self.p2.distance_to_point(_close_pt) >= tolerance:
+            return False
+        return True
+
     def flip(self):
         """Get a copy of this line segment that is flipped."""
         return LineSegment3D(self.p2, self.v.reverse())
diff --git a/ladybug_geometry/geometry3d/polyface.py b/ladybug_geometry/geometry3d/polyface.py
index 4f01a9cf..ab24cb70 100644
--- a/ladybug_geometry/geometry3d/polyface.py
+++ b/ladybug_geometry/geometry3d/polyface.py
@@ -421,7 +421,7 @@ def is_solid(self):
         """
         return self._is_solid
 
-    def merge_overlapping_edges(self, tolerance, angle_tolerance):
+    def merge_overlapping_edges(self, tolerance, angle_tolerance=None):
         """Get this object with overlapping naked edges merged into single internal edges
 
         This can be used to determine if a polyface is truly solid since this check
@@ -447,8 +447,11 @@ def merge_overlapping_edges(self, tolerance, angle_tolerance):
         Args:
             tolerance: The minimum distance between a vertex and the boundary segments
                 at which point the vertex is considered colinear.
-            angle_tolerance: The max angle in radians that vertices are allowed to
-                 differ from one another in order to consider them colinear.
+            angle_tolerance: An optional maximum angle in radians to dictate
+                whether polyface edges are colinear with one another. If None,
+                the solidity of the polyface will be determined using only the
+                absolute distance of vertices to polyface edges in relation to
+                the tolerance. (Default: None).
         """
         # get naked edges
         naked_edges = list(self.naked_edges)