1st rip a piece of duct tape about 5" long, then place the firecracker on it. make sure that there is a little sticking out. then fold over one of the corners over the fire cracker. Then tape it to the wall, after that reinforce the duct tape with multiple pieces of tape. Now tape a small piece of tape and wrap it around the fire cracker string. This will ensure a pull, instead of the string letting go and not making the firecracker go boom. Then tie the other string around the tape on the end of the firecracker.