If your garage has open rafters below the roof, you've got a wealth of storage space available above your head. By laying a board or set of boards onto the rafters, you can store many items up and out of the way. But before you begin filling the rafters with your possessions, it's a good idea to reinforce the rafters to make sure that they'll support the extra weight. You can accomplish this task with some wood and a few simple tools.
Place a ladder or stepladder against the rafters to allow yourself to climb up to them.
Measure the length of a ceiling joist from the midpoint of the garage to the wall of the garage. Divide this in two and move to the center point of this half of the joist. Measure the height from the center of the rafter directly above this point to the center of the ceiling joist.
Cut a 2-by-4-inch board to match the distance you measured. Place the board vertically, with the ends overlapping the ceiling rafter and the joist. Nail the board to the joist and rafter with two nails at each spot.
Reinforce the other half of the joist with the same method. Reinforce all the other joists and corresponding rafters you'll be storing items on.