Cut four 5-inch lengths from 6-by-6-inch piece of lumber. If your bed has six legs, cut six 5-inch lengths.
Using a 2 inch diameter boring drill bit that will leave a flat bottom to the drilled hole, drill a vertical hole 2 inches deep into one end of each block.
Round off sharp corners with sandpaper.
Stain the blocks to match the floor color. Allow to dry completely before using.
Attach a felt pad to the bottom of each block.
Remove the casters, and place each leg of the bed frame into the hole bored in each block.