Every been playing a game and couldn't be bothered holding down that button. Also can't be bothered with Macros? This is a great solution. The key-cap can sit over the top of the key and when you need it to stay down you just press and it'll stay, need to stop pressing, just lift it up. 

For standard keyboards and standard keys. Obviously won't work on special keys or the spacebar. Won't work for low profile keyboards.

There are 2 SLT, one if you have a deeper drop in your keyboard and one if you have standard.

Print notes in pictures.