A measurement from the top of the door opening upward to the lowest building obstruction on the inside of the header wall. Use this measurement for vertical clearance all the way back to the end of the horizontal track. (Commercial door application)

Amount of clear unobstructed space above the door lintel or header.

The vertical distance from the lowest point of the ceiling or soffit directly above the stair to the nose of the stair Most code require 6' -8", (80 in), (2.03 m), (203 cm)

Unobstructed clearance above opening.

The distance from the rake or tread of the stair or ramp to the lowest overhead obstruction. This measurement must be ergonomically designed to prevent head injuries. 6′ foot 8″ inches is standard; 7′ foot 6″ inches is optimum under present standards.

the vertical distance above the pitch line or the surface of the landing.

The measurement from the top of the door opening up to the lowest obstruction of the garage. Obstructions may not be above header – look into garage. 18" is ideal for a standard installation.

The distance between the bottom of the beam flange and the lower hook or the distance between the bearing surfaces of the upper and lower hooks at high hook position.

The vertical distance from the nosing (the part of the tread that overhangs the face of the riser) to any object above.

Also referred to as clearance. Refers to the total distance from a floor to the nearest obstruction above.