The new hinge installed with through bolts and lag screws into the 4x4 beam. The old jamb had a few irregular shim blocks between the trim board and corner double studs. The old hinges were bolted partially through the shims. The old blocks were cut away and a new full-height shaped plank was inserted between the trim and studs. That solid fill piece is hidden behind the old trim and the new back side plank you see here. Good thing it fit perfectly the first time because it fit so tight that it could not be removed. The back plank was added and screws were installed both ways into the studs to tie everything together. The new boards were planed and ripped at the lumber yard from clear, free of heart, vertical grain Douglas fir. In the old days to get that kind of quarter-sawn lumber the mills used to waste a bit of wood to cut those pieces out of old growth. Nowadays they just select out the cuts that are perpendicular to the grain and set them aside in the grading process.