Anonymous ID: 971f34 May 1, 2018, 10:32 a.m. No.1262509   🗄️.is 🔗kun

>>1262417

A triangle is a two dimensional object, it doesn't have a "Keystone", which is reserved for three dimensional objects, like a pyramid, for example.

A pyramid is topped by a "capstone".

Only an arch can have a "keystone".