This design is a combination of a hammer and a safety tether. Whereas it is fairly basic, this dual invention holds both a practical tool and one that can be used in emergencies to hold yourself onto another object. As seen in the model, the top part is the hammer, and the handle (which has a ruler on it) leads down to the tether at the bottom. On the side of the hammer is a loop where a rope can go. The rope should be attached to you so when you hook the tether onto an object, you’re secure. Of course, the use of these objects are pretty self-explanatory; sometimes nails may come loose, so you need a hammer to put it back in. The tether is clearly used to tether you onto something.
Hammers used on Apollo 11 and 12 were designed to chip rocks off of the moon and dig furrows. The side with the hammer head can be used for the same purpose. This object is also perfect for emergency situations- the tether is always on you, and it’s handy that a hammer is right there if you need it.