Cutting the roof off of a car isn't as crazy an idea as it sounds. It's the first step in lowering or "chopping" the roof of a custom car, and many off-roaders will remove the roof panels of off-road trucks for open-air four-wheeling or to repair trail damage. Because the roof is a significant structural component of any vehicle, its removal has immediate effects on handling and structural integrity. Cutting the roof off of a car to make a cheap convertible is not recommended. When removing a roof for a customisation or restoration job, careful planning is necessary to avoid doing permanent damage to the car's body and frame.
Remove the headliner and interior trim panels from pillars with the Phillips screwdriver or socket set, whichever is applicable to your car. If the seat belts are mounted to the B-pillar, disconnect the assembly from the floor.
Remove the tailgate by unclipping the hydraulic struts using a flat blade screwdriver and unbolting the hinges with the socket set -- this is applicable to hatchbacks, estate cars and SUVs.
Use masking tape to mark the locations where you want to cut the roof. Leave at least three inches of metal above the windshield, and at least two inches if you plan to do additional bodywork where the roof has been removed.
Remove any windows that are not mounted in the doors, including the rear windshield. Use the screwdriver to remove any exterior trim pieces, and then carefully separate the glass from the glue holding it in, using a razor blade to scrape the glue away from the glass.
Assemble the 2-by-4s in the shape of a door inside the car, just behind or above the front seats. Cut them to fit as closely as possible and use them to support the roof as you cut the pillars free.
Cut the rearmost pillars (C or D, depending on the vehicle) first, using the reciprocating saw or jigsaw. The large rear pillars may have a boxed inner section that will take some time to cut through.
Cut from back to front, removing all of the pillars.
Cut across the roof above the windshield.
Lift the roof free of the body; do this with the help of a partner.
Terminology: "A-pillar" refers to the roof supports on either side of the windshield. The "B-pillar" is at the rear of the front doors, and the "C-pillar" is at the rear of the back doors in a four-door car, and the rearmost pillar in a two-door car. Estate cars and SUVs will have a "D-pillar," which is the rearmost roof support. If the roof is not going to be reused, the wood support pieces can be screwed directly into the roof to keep them in place. If using a reciprocating saw or jigsaw, stop frequently to prevent the blade from getting too hot. Overheating will cause it to bend and break.
Driving a car with the roof removed is extremely risky; convertibles have additional support welded into the body to make up for the lack of a roof, and without these safety measures a chop-topped car will have an extremely unpredictable ride. The tailgate is a heavy component and should be supported by two people when removed. When the final hinge is removed, it may twist or drop suddenly. Do not attempt to force or twist any windows free, as they will shatter if too much force is applied. It is safest to go slowly. Never pull a corner of the window more than an inch and a half away from the frame before the glue has been removed. Cut metal is extremely sharp; be mindful of the freshly-cut pillars as you work your way through the job.