Amalgam is a great material because it’s not technique sensitive. When done well it stands up to quite a bit of abuse and hostility from the patient. Here we can see the whole distal dislodged. And while I can’t remember it ever happening to one of my buildups, I want to prevent it from happening. So I began, when reasonable making a portal that ties the distal component to the internal frustum core. A massive macromechanical retention feature. The result is this little triangle of tooth coronal to the circle in the second image. And yeah, I usually bond these big amalgams for belt suspenders as well as maybe some anti fracture attitude. The early portal cases naturally led to the double entry truss cases that followed.