1. What the assembly look like?

 
2. What they are called?
Door holder, door stopper, door magnet
 
3. What is their main use?
They are mainly used for Suction. The magnetic assembly would suck the door when the door is open so that the door would not swing with the wind or crash.
 
4. What they make from?
Most of door holders are make from strong NdFeB magnet while some make from ferrite magnet.
 
5. What shape are they?
Most of them are round and square. And their shapes also depend on design. Irregular shape is also producible.
 
Tags: magnetic assembly, door magnet