This is a one way ratchet that at the moment functions in a clockwise direction. To print a second ratchet that can function in the counter-clockwise direction, the ratchet and ratchet gear STLs simply need to be mirrored to create a counter-clockwise ratchet. The gear pin and ratchet cover do not need to be mirrored since they are symmetrical and do not affect the direction of the ratchet. This ratchet is a first build, so keep in mind that everything may not work perfectly like a commercially manufactured ratchet. For the purpose of making tool attachments, the ratchet head is about 12mm x 12mm. NOTE: The description above has been corrected from my original post. Originally I said that it functions in a counter-clockwise direction, but the STLs are actually designed to create a clockwise ratchet. The images of the ratchet I printed out are of a counter-clockwise ratchet. First, take note that there is a small opening and a large opening on the ratchet. Inside the large opening is a small rectangular inlet, this is where the gear pin is placed. Super glue can be placed on the gear pin and inlet to attach the gear pin to the ratchet for additional reliability. Next, the block on the ratchet gear is placed through the small opening of the ratchet starting from the large opening. Lastly, the ratchet cover is placed over the large opening of the ratchet to cover up the parts inside the ratchet. Depending on print quality, plastic may need to be shaved away (by a knife or similar tool) for some parts to fit together.