Breaching the Mail

Stiff fibers of the mat released my belly. Morning patrol began at the front crack. A flat, rigid white slab lay slanted across the floor tiles, dropped straight from the exterior slot. Paper boundary. Unacceptable intrusion. I lowered my skull, dug hind claws into the grout, and drove forward with full mass! Shhhk! The thick envelope skidded, crumpled against the baseboard, and pinned beneath my snout. Territory cleared. No foreign flat slab bars my perimeter.