To screen rocks and lumps out of the soil, sand, and leaf mold you use for seeding and potting mixes, you need a good garden sifter. A sifter is no trouble to make -just four 1 by 3 wood sides and a piece of galvanized hardware cloth (¼-inch mesh screen stapled across the bottom). But if you add an overlay of thin plywood or hardboard around the outside, you will improve it in these three ways:
The overlay gives a lip that holds the screen on your garden flats. It also covers the sharp edges of the wire screen. And it keeps the nails in the corners of the 1 by 3 box itself from loosening after usage and weathering.
Make the 1 by 3 box just VA inch larger than the size of your garden flats. Tack the hardware cloth to the bottom, being gen-erous with staples. Then nail the overlay of ¼-inch plywood, hardboard, or wood over the sides.
Stir soil or leaf mold with a trowel or a tool to sift it; or shake the sifter lightly being careful not to spill soil over the edges.