Two square pieces of 3/4" ply and 4 - 3" swivel casters I got from
Grizzly's Summer sale (something like 150 lb. rating on each and for
like $2-3 each). I put the locking type on the front. Doesn't move
except when I want it to and total price was around $12 (ply was
scrap).
Cheers,
cc