More models for choice:

The magnet is welded with the steel handle and levitate in the steel box, while push the steel handle, the magnet will sink to the bottom and catch iron steel. Someone have to use a crowbar if he has to remove the concrete magnet.
Shutter magnet for precast concrete, could used on plywood formwork that for concrete buildings, the shutter magnet have a huge magnetic force that could hold the concrete formwork system very tight to the concrete structure, hence the magnet for concrete formwork could do a good performance to the architecture designs.
Someone who use the magnetic formwork system need to push the round handle button, the magnet will sink and catch iron steel parts. After use the shutter magnet box, someone could use a crowbar tool to pry up the round handle button, and the magnet will return to a levitation situation and he could remove the shutter magnet.
The shutter magnet is made of big block neodymium magnet and steel, its structure is trimly welded that magnetic force could be concentrate to the bottom side. There are two hex nus on the top which is used to fix on steel structures. By using precast shuttering magnet, the time cost on estimate the dimension and measuring the architecture could be reduced, the building would be more accurate. By using precast shuttering magnet, workers could reduce the scaffold workings that are dangerous.