To aid in the ratchet ability, I modified it to include a tine (the longer stick) that gently brushes along the top of the wheel. The other end of the string is then tied to the ring. The spring pulls the string back over the teeth of the wheel after each pull. One end of the string is tied to a spring (could be replaced with a rubber band) and the spring is connected to the case. The string has a knot in it that catches with the teeth of the wheel. As can be seen in the 2nd picture, the wheel has a layer cut out to allow the string to be pulled through the wheel to turn it. On the top side of the wheel, there is an 's' shape (the two fins). It is what converts the rotary motion into linear motion. In this piece of the mechanism, the circle piece that I had printed has a knob on the bottom to shift the shifter with each 180 rotation. So each 180 degree rotation brings the shifter forwards and then the next actuation brings it backwards. The natural action for this is to use a circle which rotates 180 degrees with each pull of your finger. The final mechanism now is to get the blade to actuate both in and out with the same movement. You should be able to slide the shifter forward and backwards along the tracks in the case at this point and tyhe blade should launch out and in smoothly. I am going to break this step into multiple parts so the pictures appear more relevant. I give this advice in case you are making the mechanism by hand instead of using 3D printed parts. If they don't, you may have to re-make the paddles. Make sure the paddles fit snuggly against the blade with maybe 1-2 mm of open space between the paddle and the edges of the blade's butt. To correct this, either mirror the blade I have shown or carve by hand the proper shape and build up and missing material by glueing an appropriately shaped piece of wood to the blade where you want to add material. Also, in case you are following my 3D printed parts, I must point out here that I printed the mirror image of the blade that I needed. If it doesn't feel this smooth, use some very fine sandpaper to smooth it down. It should glide very smoothly (it should feel like it floats) through the track. Once the pins hold the paddles in place, slide the blade into the case as well. You will need to use 2 paddles one for each end of the case. If you need to, it is easy to cut one out of the modeling wood. If they are too small for your pins, you may need to use a micro Dremel bit to bore them through. The holes in the paddles is already printed into the piece. The first step to assembly is to pin in the paddles into the base case. I have included a short video explanation of how the mechanism works. They all fit together smoothly when done right. It is a lot easier to visualize the assembly with the pieces in front of you.

Assassin creed hidden blade blueprints