What is the size of the mounting bolt of the Universal Mounting Plate? Ed Clausen February 11, 2021 18:01 Updated It is a ¼”x20 standard thread. This is compatible with all AbleNet mounting systems. Related articles How do I connect a mounting plate to the Friction Knob UMS? How do I install the locking knob on the Universal Mounting Plate? The colored switch cap comes off while using the Big Red. Is there a way to secure it so it doesn’t come off as easily? Comments 0 comments Article is closed for comments.