Pool Cover Specialists 87505 3 Pack of White Thread for Pool Cover Repair - This replacement thread assists in repairing holes in pool covers. If water penetrates the cover's vinyl and is exposed to the scrim (the thread-like reinforcement), the scrim will soak up water; carrying chemicals and contaminates to the inside of the fabric. This can lead to discoloring, stiffening or deterioration of the pool cover. Repair both sides of the hole in the pool cover when possible with this thread.