I inherited XL 9100 from my mother in nursing home. Using this manual on line. I disassembled roller etc to clean out wound thread, dirt, etc. Cannot seem to re-insert belt, which has a square hole in it????? If I replace the belt completely I still don't know how to insert belt????? Where is "manual" that this Users Guide refers me to on p. 5 of this user's guide???? Lucy S.