This is a very useful tool. It allows you to store experience. Only two rooms:
In one room, the experience can be put in the bank.
In another room, you can take experience.
To put or withdraw experience, simply right click on the sign.
Working on a server! Every player has his own score (take another player experience is not possible). To see how much experience on account of the players need to enter the following command:
/scoreboard objectives setdisplay sidebar exp
Warning! Display the player's accounts only after you have once put or will take the experience of the bank.