Senior engineering technician Carl Lowrey describes a trick to make sure filleting polylines in AutoCAD works the way you want it to.
"Ever tried to fillet between two polylines, only to get the fillet trim the wrong way?
"Try this: Reverse the direction of the polyline that misbehaves. Right-click on the misbehaving polyline and select Polyline > Reverse (or type Reverse) and fillet again.
"This trick works in all versions of AutoCAD since 2010."
Notes from Cadalyst Tip Reviewer Brian Benton: Polylines can be fickle, especially when you are trying to edit them with the Fillet command. This reverse trick works. I set up a drawing like the example, but couldn't repeat it until I tried to fillet the other end. It wouldn't work until I reversed the polyline.