The Harris Bipod Adaptor has a rectangular piece with a female threaded nut that fits inside the handguard on top of the heat shield. After the bottom handguard is removed it is placed in the second vent hole back from the front on carbine handguards and the third hole for standard handguards. A smaller rectangular washer fits on the outside of the handguard and the stud is installed until it is tight. Reinstall handguard to upper receiver assembly.
The stud comes with a Quick Detach swivel attached. Turn the knurled section counter clockwise then push on it to release the leg on the other side so that is turns down allowing the swivel to be detached. Install the bipod onto the stud. There is a place on the bipod to install the QD swivel. After installing the swivel turn the knurled section clockwise to lock it in place.