The retractor is used for surgery to hold the wound or incision open so they can do surgery. Surgeons use this to remove items from people's bodies. The design is like a pair of scissors, but it has a longer cross and flats used to hold open the an incision. This will be helpful Mars in the event someone needs a surgery performed. The retractor has two rings to hold the it sturdily. The sides tilt down where the flats are. In the middle of the retractor, it is shortened to keep the sides even. The center of the retractor has a hole in which you can put the pin inside it to hold the two pieces together. Without the use of the retractor on Mars, you might not have anything to hold the incision. It should look like scissors. I recommend to make this out of plastic to keep this more sturdy. To use the retractor, spread the two rings with your thumb and pointer finger. Make sure you are holding the rings. The retractor could be mandatory on your three year journey to Mars.