Drawbore peg
A tapered oak peg that draws a tenon home and locks it forever.
The peg is the quiet hero. A tapered oak pin, driven through a slightly offset hole, that physically pulls the tenon tight against its shoulder and then just… stays.
Drawboring
drill the tenon hole 1/16" proud of the mortise taper rive the peg square, then shave it round drive the offset pulls the tenon home as it seats trim flush, or proud for the look
Why it works
Steel rusts and loosens. A peg swells with the wood around it. The whole frame becomes one piece, over a few dry summers.