Whether you view yourself as the next Rocky Balboa or you're just adding kick-boxing to your fitness routine, putting a heavy bag in your basement or garage will let you train without having to leave the house. If you have room for a weight bench, a rack of plates and a speed bag, you'll basically have a home boxing gym. Tethering the heavy bag correctly will make your boxing training sessions safe and effective.
Hang the bag from the correct height. Each heavy bag is somewhat different in the location of its "sweet spot." This is the place in which, when you hit it, it will "hop" away from you. If you're hitting it too high, it will be too easy; too low, and you won't get the benefit of your punches, because the bag will just spin around. The sweet spot should be right by your eye-level.
Secure the hanging bag into a joist in your ceiling. Most bags come with the necessary hardware, so follow the installation instructions. Most kits have a set of heavy screws that go through a metal plate that has pre-drilled holes. You'll need to drill the holes in the ceiling joist with a drill, then put your screwdriver bit on and tighten the screws.
Attach a cord to the bottom of your heavy bag. Most bags have a metal ring on the bottom, and some have a cord or strap already attached. Set a weight on the floor -- this could be anything from a dumbbell to a 25-pound free weight plate -- and attach the cord or strap to it.
Tug on the cord or strap to give plenty of slack before securing the final knot. The bag should swing as much as a foot in either direction. If you strap it too tightly, you won't get the proper response from the bag, which is designed to help you with timing.