Answer by Lee Sam for Attaching double 2x10 beams to 4x4 post

You are describing “column caps”. They are used to attach beams to columns (posts) and come in many sizes.

You indicated you’re looking for a triple 2x beam attached to a 4x4 or 4x6 post. See Simpson chart below for correct size:

https://www.mudsupply.com/simpson-CCQ4-62-3-62SDS-p/999957728.htm?gclid=Cj0KCQjw2tCGBhCLARIsABJGmZ6FOJ0PtHqFnw7gU6vxuFp_vVct_Yqyn_R5HGtwKL1T8AFfom096ycaAswgEALw_wcB