This is a guess since I've never used a truing stand without it being bolted down but I don't see how that is possible. The center of gravity when the wheel is mounted is going to be high and the whole assembly unstable. If you won't or can't permanently bolt it down, at least C-clamp it to a table or bench top. Perhaps bolt it to a piece of 1/2" or 3/4"plywood and clamp that base to a work bench.