Honestly I do not know what these other reviewers are complaining about. The locking lip has to be folded parrallel to the body of the pump, not sticking out. Press the pump down on the valve HARD with the lip/tongue out and then fold it down. Pump, Pump and Pump some more; it takes a lot of work to get a flat up to even 35psi. 50 PSI? Forget about it. But I use this on my travel gear because its light and easier to yeild than carrying around a floor pump or kick pump. I save the heavy equip for home; happy trails.