Measuring Tape Metal
There is a tiny metallic piece on the end of the measuring tape. It has been added there for a number of reasons. If you are working by yourself, you can wrap this bit to a nail to hold it in place. Aside from that, the edge is serrated. This is useful if you have to mark the surface.
Pen Cap Holes
Pen caps are often designed with a hole on the top. Why did they do this? Apparently, it was meant to allow air to flow. In case you swallow it, you should be able to breathe just fine. Considering how many people chew on their pen caps, this is probably for the best.