This is my second one of these and I'm still not impressed by the three screws which invariably loosen with playing. I need to tighten them every time, it's part of the pulling the end-pin out routine. It doesn't lock. Using pliers to tighten as much as possible helps but that is really going too far. There is a slot so that you can use a coin or a screwdriver but it isn't deep enough. There are cheaper end-pins which do stay tight but their rubber wears out much quicker. At least with this, the rubber keeps going for many years, the rubber wearing out problem with others is such that when they go, the bass just slides away and this is most disconcerting. Still looking for the perfect one.