This has to be the simplest pivot system in the world.
The top pivot is surface fixed to the underside of the finished head.
The bottom pivot is surface fixed to the finished floor.
The newest 'Angle-Shoe' TR35 pivot set is for builders in a hurry.
A tiny transom 35 x 10 houses the top pivot and concealed magnetic catch.
It's for 2040 x 870 x 35 bedroom and bathroom type doors.
(For those with old world charm - 6' 8" x 2'10" x 1 3/8")