The most likely explanation is that as we began to mass produce doors the centre of most middle rails in the typical drop panelled door was 36 inches from the bottom of the door.
Standard bore height for door handle.
Most interior doors are prepped with a single boor hole.
All handles pulls latches locks and other operable parts of the door should measure between 34 inches and 48 inches above the floor.
Why this is standard is not certain.
Exceptions to the rule include doors that provide egress into swimming pools or other water features.
The standard sized bore hole is 2 1 8 in diameter.
The requirements of bs 8300 provide for a door knob to be between 800mm 1050mm 31 5 41 5 inches from a finished floor.
Standard height the standard height for doorknobs on a typical 80 inch tall household door is 36 inches.
The standard measurement for a bore hole is 2 1 8 inch in diameter and the standard measurement of a cross bore is 1 inch in diameter.
This cross bore is where the latch is installed.
Their position should be between 900mm 1050mm 35 5 41 5 inches above the floor.
Through the edge of the door there is a 1 cross bore that extends from the edge of the door through the bore hole.
Generally the knobs should be of a free moving slide action.
The international building code has established doorknob height between 34 and 48 inches above a finished floor.
The latch bore is the small hole on the edge of the door for the latch itself.
The bore hole is the large diameter hole where the door knob is mounted.