DISPENSERS

you can use dispensers for a lot of different things the main one being a defence mechanism for your base this works much like the pitfall one in my previous post but you fill it with arrows instead and it will not push back any mob but can do damage you place a pressure plate to them via a redstone wire and on top of this place a button on the floor behind it, it will spawn onto the back of the dispenser meaning you can simply click on the dispenser to activate it if the mob miss the pressure plate