[ithacaartist]

Another method I use is to insert an empty mag once the upper is slid on and the hook properly engaged. Pull back on the toggle knobs and it will lock back with the hold-open, allowing installation of the side plate and subsequent rotation of the locking bolt. This eliminates the juggling act required to do these operations with one hand while maintaining all that pressure with the other--a setup which is inherently unstable and may slip if you're not careful. Afterwards, remove the mag, cycle the action, de-c0ck, and you're good.