Abstract: A cover for use with sacks for covering the mouth of a sack after it has been filled, to prevent its contents from spilling. One application is for recyclable yard waste sacks that are used to carry yard waste such as leaves, or used for carrying food scraps from restaurants. The sacks being made of paper so that they can be composted, require a cover that is made of paper that can be recycled as well. Some embodiments of the cover utilized a paper with a plurality of holes or die-cut slits that stretch into a hexagonal three dimensional shape when pulled, and contracts when released. The unusual elasticity afforded to ordinary paper by the slit holes patterns is used to create a sack cover that can stretch to close a sack without tearing. The elasticity is utilized to create sufficient griping force on the mouth of the sack to resist dislodgement of the cover when the sack tips over. A few embodiments of the cover utilize a hybrid design in which both ordinary and slitted paper are used.