If you’re planning on using your magnetic sweeper in grass, consider the ability of different sweeper options to deal with “wipe off”.
“Wipe off” occurs when grass or weeds brush the bottom of the sweeper and the debris attached to it, causing the debris to be pushed backward on the bottom of the sweeper.
If the debris gets pushed far enough backward and out of the magnetic field of the magnet, the nails or debris you picked up can fall off. This can happen with many magnetic sweepers that have a magnet inside a housing, where the magnet is much smaller than the housing.
At Bluestreak we design some of our magnetic sweepers with a “Wrap Around” feature specifically to deal with this problem. If debris gets pushed backward, it simply snaps around onto the back of the sweeper and isn’t wiped off.