1 - Put belt through belt loops.
2 - Insert tail of webbing through buckle (locking rod should be between the webbing and your body).
3 - Pull tail of webbing through buckle until the belt is slightly too tight on your body.
4 - Push locking rod into position to SET buckle.
5 - While gently pushing locking rod towards the locked position, pull HARD outwards on the belt like you just magically got 100lbs fatter). The belt will slip a little (about 1/4 to 1/2 an inch) as it locks, but once locked, it absolutely will be locked down until you UNLOCK it.
NOTE - If the bar is not ALL THE WAY at the end of the track, it COULD be locked tighter. It almost certainly doesn't NEED to be that far down, but if you're still experiencing slippage, lock it tighter.
To UNLOCK an Aegis belt, just pull the tail away from the buckle (tighten the belt on your body) and the bar will pop loose. Then remove tail from buckle.