Thought I'd pass this on: If you assembled your BB as a kit, you remember what a pain in the ass the "poke grub screw through grille slots to secure Y-axis belt" routine is. I wish Greg had come up with a better arrangement, but it's what we've got. I found the front left and back right grub screws especially troublesome because their (right-hand) threads tend to slacken the belt and reduce the amount of grip available. I've had a belt slip out of its mooring partway through an umpty-hour print, so after a bit of head-scratching came up with something that holds them in place. I simply painted the ends of the belts with water-based contact cement (figuring solvent-based c.c. might be bad news on either the rubber or the plastic), let it dry for a while, and re-inserted them in the slots. I let that dry for a while, then screwed in the grub screws and let the whole arrangement dry thoroughly before tensioning the belts. Nothing moved while I tightened those @&!# grub screws, and the belts have stayed put ever since. If you've had similar troubles with your Y-axis belts, this is an easy and cheap fix...and no worries that they'll be permanently attached: contact cement only forms a permanent bond when both surfaces are coated and allowed to dry.