Yes, I have held mandatory office hours and conferences; in fact, I held nearly twice the required amount of time for office hours for the first part of the semester. Barely anyone came and I eventually had to cut my hours down slightly to accommodate for an important obligation, but I'm still holding well over the required time. On the most substantial assignments, I grade by rubric so there can be little question of my reasoning and thereby also create a "paper trail". I do try to keep my office door open, but students have shut it behind them in conferences before. I am planning on getting a doorstop or something for that reason, and now plan on instituting a "conference log" for student visits.