Hager RC1542 4 x 4 US10R NRP

A: That set screw in the middle of the hinged is a security feature that is called NRP which stands for non-removable pin. This type of hinge is used most commonly specified and used when you have exterior doors that swing out exposing the pin and barrel assembly of the hinge to the exterior. The function of the NRP feature is to simply eliminate and prevent someone from driving the pin out of the barrel and very simply removing the door from the frame. An exterior door that swings out would be very simple to remove by anyone with simple tools without this feature. Very occasionally someone will intentionally install a security hinge on the interior of a home as well so as to deter the tampering of the barrel and pin. Conversely you may very specifically not want to use this sort of security feature if you have the expectation that you may need to remove the door from the frame in this regard. I would recommend a client to not purchase this NRP feature if they simply have no need for the level of security that it provides as this feature simply only marginally drives up the cost per hinge.