Question: Why does the hook move on a tape measure?
Answer: The hook on your tape measure moves to ensure accurate measurements.
Why a Tape Measure Hook Moves
Movement in a measuring device may seem counterintuitive to accuracy, but hook movement is actually an important feature when it comes to tape measures.
Notice that when you move the hook back and forth, it moves the same distance as the thickness of the hook.
When you’re measuring material, say a sheet of plywood, you let the hook grab the end of the wood and pull the tape across it. When you do that, the hook shifts out slightly, ensuring that the zero point is on the back of the hook.
Sometimes you have to measure an object you can’t grab the edge of with the hook, like when you’re measuring the distance across the floor to the wall. In that case, you push the hook against the wall. Since the thickness of the hook is now included in the measurement, it has to move to make up for it and shift the zero point to the front.
In short, the hook on your tape measure moves so you get an accurate measurement no matter which side of the hook contacts what you’re measuring.
Tape Measure Hook Accuracy Issues
There are times when your tape measure legitimately isn’t accurate, though. The most common failure is when the hook gets bent slightly. A tape measure calibrating tool can help you bend it back to the correct 90° position.
Occasionally, you might get debris around the rivets or stuck on the hook. If it gets to the point where the hook can’t move or it adds thickness to either the front or the back, your measurements won’t be accurate. Sometimes you can clean it off and get right back to work. If not, it’s time to get a new tape measure.
A third possibility is that the blade printing is inaccurate. It doesn’t happen often with quality tapes, but we have come across a few that were off. If you’re not sure, a tape measure calibrating tool can reveal the error. Alternatively, you can line it up side-by-side with a tape you know is accurate. If the printing is off, bending the hook won’t fix it. Either see if you can get a refund/exchange or toss it.
If you’re in the market for a new one, check out our best tape measure recommendations for the year.
Like the look of the one we used in the photos? It’s the next-generation Milwaukee Stud and it’s super-durable. You can pick one up for $29.99.
