Obtain the dimensions for each window. Measure the distance, from side to side, between the inner frame window trim pieces, or stops. Also measure from the head jamb to the bottom windowsill.
Plan the design with either frame with grid or a supported grid construction. The frame with grid design consists of a square, or rectangular box with vertical bars welded in place every 4 inches. The supported grid entails vertical bars spaced 4 inches apart with horizontal bars welded to the vertical bars every 12 inches. This design does not have an outside frame.
Calculate the amount of material required to construct the burglar bars. Purchase iron, angle iron, flat bar stock and square tubes. Form the sides of the burglar with the angle iron. Use the flat bar stock for the top and bottom components and the square tubes for the vertical bars.
Cut the angle iron and flat bar stock with an angle grinder. Weld the frame for the burglar bars. Cut the vertical bars to the appropriate length. Position the vertical bars on the frame, spaced 4 inches apart. Have the supplier or local iron shop cut the materials into the desire lengths to avoid having to make the cuts.
Check the vertical bars with a framing square to ensure the proper alignment in the frame. Place the long blade along the inside of the vertical bar and the shorter blade on the top edge of the lower rail of the frame. Mark the locations of the vertical bars on the interior surface of the top and bottom rails of the frame. Weld each of the vertical bars to the frame. Drill three holes for the fasteners into each side of the frame. Use a high-carbon steel bit and cutting oil. Rent a drill press to make this aspect of the job easier.
Spray the completed bars with a coat of primer, enamel and enamel hardener. Follow the manufacturer's instructions for installing the quick release safety mechanism. This device consists of button on the inside that releases a locking pin on the bars.