First of all you need a red color lengthy piece and insert a four cm long rod inside the second hole from the top. Now you need a gear wheel and fit it into the rod. Now take a connector piece and put it also in the second hole from the gear wheel. Now you need a piece which is 'L' shaped and put it in so that it stops the gear wheel from moving. Now take two more connector pieces and put in the red lengthy piece at the bottom two holes. Now take another black color lengthy piece and connect it. Take another red color lengthy piece and put it across the two connectors as shown. Note that the gear wheel shall be inserted in the second hole from the top. Now take another four cm rod and fix it like a trigger. Now you need smaller pieces as shown in the video. Now take your gun and put the black piece in the first hole. Now place the connecter in the second hole. Put the white piece in the third hole. Add more pieces as shown. Now put the handle and turn around and place the second handle. No put the connector pieces into third hole from the top. Now your gun is ready. Take a rubber band and put it on the let off, and bring it over the connector piece and bring it over the gear wheel as shown. Aim and then pull the trigger. That's it.