What it does?
You put items in and it acts like an auto dispenser, except if you put the right item in it will output a signal which you can connect to whatever you want, very small and easy to change the key/keycard.

Uses -
1. Houses that requires a key to access.
2. Adventure maps that acquire searching for a key to access the next room, good because you don't need to worry of losing your item once you put it in.
3.Your imagination is the limit!

Note : You probably should watch the tutorial for this build.

If you like it, give it a diamond or a comment.
want to see what I'm up to ? twitter.com/RedstoneMagic
If you don't like it, your opinion, give me a reason why you dislike it in the comment section.
Have fun, create creations, compact if you wish and see you later!

-RedstoneMagician