The question is not whether the walker fits the house in general. The question is whether it fits every room on the route Dad takes every day, including the turn at the end of the hall where a frame is most likely to catch. Measure the route, measure the equipment, then compare the two numbers on one card.
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Map the route before the tape comes out
Walk the route from the bed to the bathroom, the kitchen, the front door, and the side door. Note every place the path narrows: each door opening, any corner, the gap beside a recliner, and any laundry basket left in the hall. Those are the pinch points, and they are the only numbers that matter until proven otherwise.
Measure the narrowest point
At each pinch point, measure the clear width between the door trim or the walls, not the width of the door slab. Use the narrowest reading. Note whether the door swings into the room, because a door that swings in takes space from the path while it is open.
Measure the equipment at its widest
Measure the walker or chair across its widest part, including handles, brakes, and wheels. Then measure how much room it needs to turn at the corner. Write three numbers on the card: the narrowest doorway, the widest part of the equipment, and the turn at the corner. Compare the card to the equipment's listed size, not to a guess.
Decide what changes
If the equipment does not fit, the choices are a smaller or narrower piece, a different route, or a change to the door or opening. Moving a chair or a basket is cheaper than changing a door, and it is often the first fix that works. Decide which of those you are willing to change before anyone orders anything.
Next move: walk the route from Dad's bed to the bathroom with a tape and a pencil, mark each pinch point on the wall, and measure the narrowest one first.