I have recently purchased a door way pull-up bar, however the trim on one side (referred to hereafter as the "back" side) is not thick enough for the pull-up bar's (unable to find official nomenclature here)
The back trim is flat, unfinished wood. How can I increase the depth of the trim such that it will be safe to use the pull-up bar in the doorway?
Simpler is better given limited access to tools (namely, a hammer).
Below is a picture showing how the pull-up bar mounts in a door frame.