Chamfer (1 Setback Value) (2D)
Insert 
Geometry Chamfer
(Sketch/Sheet Level)
Use this command to create
a chamfer of equal setback values between two curves. The setback is a
straight line distance between the vertex and the new setback point.(i.e.,
intersection of the curve with a theoretical circle with a radius equal
to the setback value and centered at the vertex).
Select the two curves near their ends to chamfer and then
specify the offset distance.
Extension
Use this option to control the path of extended curves and faces.
Linear - The extension follows a linear path.
Circular - The extension follows an arc path in the direction of curvature.
Reflect - The extension follows a reflective path opposite the direction of curvature.
Trim
Use this option to trim (or extend) curves.
Trim both - Trim/Extend both curves.
No trim - Add the fillet or chamfer without modifying the existing curves. No trim/extend is performed.
Trim first - Trim/Extend only the first selected curve.
Trim second - Trim/extend only the second selected curve.
