Every light or laser manufacturer designs the parts to fit a specific way. Instructions are always sup[plied. Us (people) being who we are we tend to ignore those items and do it our way. Usually end up looking back at the instructions though.
The proper Key allows for the Light to be placed on the rail of your pistol with the exact placement that it was designed for. The Key is designed to fill the space on the rail and place the light body at the proper placement for your fingers and thumbs to access the light switched on an ergonomic fashion.
How many time have you seen one of your friends or people you know put a light on the pistol, that hangs way below the trigger guard? Puts the activation switches or buttons in a position that makes the Firing grip loos its placement to reach the switches.
Just because you bought a light it may not be designed for the type of pistol you have. The usual thoughts of Big pistol, Big light, may not apply today. But the designers thought these out pretty good on the major manufactures. Choose wisely when you decide on a light or laser. Stick main stream brand and you will find more industry support for it. Holsters need to be made for the Pistol mounted Lights. Easier to find good quality Kydex type holster when you stay main stream.
Look for Kydex holster support before you decide on a light or laser. Make sure somebody manufactures one. Make sure you are not building a unicorn. Check out our holsters with lights on our webstore.