The 4 hole - square flat plate is an external fastening method that requires no machining services. It is a durable connection that can be repositioned and reused. This connection can provide infinite positioning along the profile T-slot, allowing for a large degree of adjustability. The 4 hole - square flat plate engages the 2-degree drop-lock feature when the assembly bolts are tightened to the required torque, creating a strong connection. Tip: Use a double slide-in economy T-nut to save time and money. Pre-load your hardware prior to connecting profiles to simplify your assembly.