Stayput Black Attachment Knobs for Shock Cords used with Canvas Covers, 10 Pack Stayput Black Attachment Knobs for Shock Cords used with Canvas Covers, 10 Pack 10 Pack of Black Shock Cord Attachment Knobs Look for our Pull Cord to stretch the Shock Cord onto the Knob! Quick & Easy to Use! No more tired fingers from Snapping on Covers!