You can use LEGO pieces to create a realistic plastic replica of a butterfly, or balisong, folding pocket knife. It's safer than the real thing and certainly less expensive.
Take two of the 12-hole connector pieces and lay them so the holes are pointing up. Grab the three-hole-length connector piece and three of the four-hole-length crossbars. Place the cross bars in one end of the 12-hole connector piece. Each crossbar will have its own hole to snap into. Slide the three-hole-length connector piece over the crossbars. The top of the crossbars will still be visible. Snap the second 12-hole connector piece onto the crossbars. The pieces will be U-shaped now. This is one part of the handle.
Grab your other two 12-hole connector pieces and two of the four-hole length. Skipping the first hole, place two crossbar pieces into the end of one of the connectors. Slide a two-hole cross piece over the crossbars. Take the three-hole-length crossbar and insert it through the end of the cross piece so it sticks out both sides. Cap both ends with the clear teeth pieces. Snap the last 12-hole connector onto the top. This side of the handle will help the blade stop and not continue swinging.
Take both pieces of your handle and remove one of the 12-hole connector pieces. Set them aside. Lay them on your work surface so the sides with the exposed crossbars are pointing up.
Take one four-hole-length crossbar. Also, grab the one-hole connector and the two one-hole cross pieces. Slide the crossbar through the hole in the one-hole connector. Snap the two one-hole cross pieces onto the ends of the crossbar. Make sure that a little of crossbar is sticking out of the ends. This piece will look like a goalpost. Set it aside.
Make the guards next. Grab two of the two-hole cross pieces and two of the four-hole-length crossbars. Slide one of the cross pieces to the centre of one of the four-hole-length crossbars. Repeat with the other crossbar and cross piece.
Take the guards from Step 5 and place one into the opposite end of the connector pieces that still have the crossbars attached to them -- not the ones that were removed in Step 3. So, each end of the handle has one guard piece snapped into the last hole.
Snap the 12-hole connector pieces you removed in Step 3 back on top as they were before.
Take two of the one-hole cross pieces and attach one to the guards on the end of the handle pieces. They will attach to the part of the guard that you were to leave visible in Step 5.
Take the goalpost piece from Step 4 and snap it into place with the two-hole cross pieces sticking straight up like a goalpost. Attach the second one-hole cross piece so both sides of the handle are capped off.
Snap the blade into the bottom of the goalpost piece.
All of your materials can be found within the LEGO Bionicle collection.