Common J Hook
some holsters makers sell. It does not work most of the time. It slips off the belt.

As you can see from the picture, gravity and the weight of the gun will pull down on the holster towards the ground. There is only 1/8 of an inch of J hook on most designs, that has to be pulled down to slip under the belt. Physical activity will also aggravate the situation. Now when you draw, you get the holster and gun coming out of your pants. This is dangerous. The design does not work most of the time in our tests.

     High Noon Holsters Reverse J Hook
is a design that will not slip off the belt when you draw the gun. It locks on and under the belt, The weight of the gun, gravity or physical activity will not effect this clip.