Originally Posted by dobber
Define removable? Five minutes?
Depending upon the rack, I'd have a plate (or perhaps some large fender washers) inside the crate and some plates (or washers) underneath the rack. Pass bolts thru the assembly and use a wing nut.
this is exactly how I attach mine. Two plates (about 6" x 1") with 1/4' threaded bolts and wing nuts w/ washers (locking washers are good). Put one in the base of the milk crate and the other under the rack, drop bolts through and put washers and wingnut on the underside (otherwise the bolts and wing nuts poke through your bags and make holes in back packs and bags). Just tighten as tight as you can and, if you're like me and carry a leatherman, you'll be able to cinch 'em down or undo them if they're a little more than finger tight. Total cost with found milk crate: about $3.
I can easily carry two very heavy grocery bags plus NY kryptonite Lock and cable in my milk crate and have never had a problem- just make sure you've got a substantial rack that it's attached to.