For like, 5 years of smoking, I could never figure out what the bong cap is for. Now I use it to smoke roaches or sometimes pinners in one go. You just put ur joint in the hole, screw the cap on, light it, suck back, fill your bong whilst simultaneously burning the whole joint down, then take out the peice & clear the bowl. I rarely do it, but it works and can be very good for hard-to-smoke roaches. Also, every once in a while, I will roll a pinner, stick it in the choke of one of my pipes and then use the bowl as a choke in order to smoke the joint outa the pipe.

Lets just pretend thats what the bong cap is for.