Start with the largest piece of equipment or vehicle that needs to move through the opening then add clearance. Don’t just measure bumper to bumper, think about everything on the outside too. Side mirrors, items on top, and anything extending beyond the vehicle profile all need to clear the opening comfortably. A good rule of thumb is to size up rather than down. Getting the largest door frame-out you think you’ll ever need at the time of build is far cheaper than enlarging the opening later. Metal Pro’s design team sizes every opening based on actual workflow not guesswork.