I discovered this when building my first lower receiver. I was afraid that I would break off one of the tabs like every body warned against when installing the roll pin. But I was to impatient And cheap to buy the recomened front sight block I also noticed in videos it still didn't provide a lot of stability either. I looked around the house for a substitute I found a cap from a vitamin water bottle same as a Gatorade cap not only was the right size but maso that the receiver was completely stable. I'm not sure if this has been posted before but hope it helps people in ther own builds!!