High security contacts use 3 form-C relays within each contact. These are VERY sensitive and must be position correctly to obtain the maximum gap, which is 3/16" minimum to 5/8" maximum. The pictures below show the proper orientation of the contact and the magnet. Be sure to read the installation instructions before starting your installation. Any installation you perform will be very close to both figures A and B. Any variations greater than 1/8" may lead to reduced gap.
ALWAYS use your ohm meter to verify positioning of each piece. Variations in the thickness of the metal, type of metal and other factors can affect the exact alignment.
Never use a sheet metal screw to secure either piece. Sheet metal screws can break in the metal and removing them is sometimes impossible. Even if the screws go in correctly, they can break on removal. Since exact alignment is needed you must always use a #8/32 tap kit to drill and tap the metal. Then use machine bolts to secure the devices. Never use a drill to drive the bolts. You must always install the bolts by hand. This assures the devices are secure and at the same time easy to remove for servicing.