Understand the sliding hook
The metal hook at the end of the blade moves by about a millimetre. That is not sloppy manufacturing. It is the thickness of the hook itself, which allows the tape to give a true measurement whether you are hooking over an end or pushing against a face.
Do not try to fix this by bending the hook flat or by always adding a millimetre. Trust the design and read the number the blade gives you.
Read fractions at eye level
The most common reading error is parallax. If you read the blade from an angle, the marking you think lines up with the edge is not the marking that actually does.
Bring the tape up so the graduations are at eye level, and use a fingernail or a pencil tip to mark the exact line rather than eyeballing a position.
Burn an inch when precision matters
For critical measurements, hook the tape at the 100 mm mark instead of zero and subtract 100 from your reading. This avoids the hook play entirely.
It feels fussy. It is also how cabinets get made square and how picture frames close without gaps.
The three quiet mistakes
Measuring the same distance twice from different references, marking with a thick pencil line and cutting to the wrong edge of it, and measuring a board while it is unsupported so it flexes. Any one of these adds a millimetre or more to a cut.
Use a knife line for joinery, mark the same reference face every time, and support the stock along its full length before you measure.
