Now take the half prepared center and mate it to a corresponding barrel on a flat surface. Be sure to press down firmly (securing it in place), then align the bolt holes.

Note: Make sure that the pieces being mated together correspond to each other's offsets. Meaning, a front barrel gets mated to a front center and a front lip. Choosing to disregard this precaution, will increase the probability of an improper fitment and an undesired offset.