Summarize the following:
Having the right tools on hand will help this process go smoothly and quickly. To bend your sheet metal with a vise and hammer, you will need:  2 wooden or metal form blocks Block of hardwood and heavy-duty hammer or mallet (optional) Calculator or online bend calculator Marker Protractor Rubber, plastic, or rawhide mallet Ruler or tape measure Sheet metal Vise You can use a tape measure or ruler to measure the thickness of your sheet metal. This measurement will be necessary for calculating your bend allowance. If your sheet metal is too thick, you may need special machinery, like a brake or a torch, to bend your sheet into the desired shape. The bending you will be doing will warp your sheet metal so that it is physically bigger. To calculate the expansion that will take place on the outside of your bend angle, you will need to know your bend allowance. You can find your bend allowance with the following formula: (π/180) x B x (IR + K x MT) =  bend allowance (BA), where B is the angle complementary to your desired bend angle (1 to 180 degrees), MT is the thickness of the material, IR is the inside radius, and K is the K-factor.  To ascertain your K-Factor, inside radius, and material thickness (expressed as a decimal), you should use an Bend Allowance Chart. As an example, if you want to bend 24 gauge sheet metal at a 90° angle, the calculation would be: 0.017453 x 90 x (0.020 + 0.33 x 0.024) = 0.0438558984 inch bend allowance Keep in mind that some metals are more brittle than others. Bending a brittle metal beyond its limits could cause the metal to snap and break. Now that you know your bend allowance, take your protractor and draw a clear line with your marker across the point at which you will bend your sheet metal. Then use your bend allowance to draw your second bend line, the intervening distance between your bend lines (bend radius). The space between your bend lines will expand with the application of your bend. You should leave a little trim to your sheet, approximately ¼" is recommended. Be sure you file and smooth your sheet, as nicks and rough edges can cause cracks to form in your metal.
Gather your materials. Determine the thickness of your sheet. Calculate your bend allowance. Mark your bend lines. Cut your sheet to size.