Flexible Tape Measure
A flexible tape measure is a great tool to add to your kit. Use them to measure around curves and odd shapes. They will also fit into tight locations. Cut them into shorter lengths when needed. Find them in the sewing supplies.
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But these tape Measures are not accurate (stretch!)
I pulled mine taut against a 48″ ruler and found it to be accurate. If I used excessive force, it stretched about 1/32″. If moderate force is used, it is reasonably accurate.
Look into Fastcaps flatback tape measure. It combines the best aspects of both the traditional tape measure and the type in the post.