Ok, i'll explain it as best I can. I wear a silicone sleeve that fits tight over my stump, on the end is a pin which fits into a lock in the leg. The pin is chamfered all the way down so that it can only go one way until the lock is released.
This is a photo I knicked from the web , my sleeve is grey but apart from that it's much the same. It's a good system for me , the only downside is when it's hot my leg sweats and this can cause the sleeve to slip hence a few mishaps where it has fallen off