Inflating a Polyform Fender with a compressor is easy when using a tapered rubber tip on a "blow gun" attachment. First, remove the valve screw plug. Next, inflate to no more than 2psi. Do not over inflate. It is better to under inflate. The fender wall should remain flexible. Finally, re-insert the valve screw plug. When flush with the surface, only tighten until snug. (Usually no more than 1/2 turn.) Properly inflated fenders provide years of service when used as intended.