Fortified Area is a common Enchantment card from Fourth Edition (4ED), collector number 26. Current market price: $0.19, TCGplayer market prices via Scryfall.
Wall creatures you control get +1/+0 and have banding. (Any creatures with banding, and up to one without, can attack in a band. Bands are blocked as a group. If any creatures with banding you control are blocking or being blocked by a creature, you divide that creature's combat damage, not its controller, among any of the creatures it's being blocked by or is blocking.)