HES 9500 Tech Tips When installing surface-mounted door hardware, establishing mounting threads in thin-gauge metal frames can be a challenge -- often requiring the installation of blind nuts to establish an adequate thread. Because of their design, blind nuts can cause surface-mounted door hardware to not fit flush to the frame. Recognizing this real life issue, the design of the 9500 electric strike has been enhanced to provide a flush mount even when used with blind nuts. If interested in purchasing blind-nuts and blind nut installation tools, seek out the Securitron BN-250 blind nut and accessories pack. To learn more about the completely surface mounted, fire-rated electric strike, please visit the 9500 product page.