A garrot is probably more trouble than it's worth, with all the attendant problems of cutting bees in half, snapping your wire, pulling your hive over (??) and what not.
I have noticed having looked at a lot of very old boxes that they tend to wear out at the corners, top and bottom, and I suspect this is due to prying them apart with a hive tool. They get chewed up and a gap forms, then naturally you use that gap to stick your tool in and it gets larger, etc. A piece of sheet metal to reinforce the corners and give some protection from the prying hive tool might make sense...