These plaster bricks have a flat back for easy installation and since they are plaster, they are easy to cut with an exacto knife and you can use sandpaper too. We recommend gluing these down with a white glue first. Dry. Then spray them with a matte finish sealer. Dry. Then grout in between with mortar, we use Magic Stucco. Dry. Spray again with matte finish sealer. Each brick size: 9/16L x 3/8"W x 1/8"."