The headliner is the part of the car which acts as a ceiling. You should promptly repair the headliner if it is torn. The headliner is usually upholstered, and its job is to keep your head away from the metal of the car roof. However, it is easily damaged, and this can mean that you have an unattractive piece of material flapping around your head as you drive. In order to solve this problem, you need to repair the headliner as soon as possible. You can perform a quick repair, and then try a more permanent one when you have more time.
Step 1 - A Quick Fix
If you need to repair the headliner quickly and without too much effort, try twist pins. These will hold the material together for a short period of time. You could also use tape to keep the headliner together, although both of these solutions are not necessarily very practical when it comes to performing a long-term repair. These are simply on-the-go solutions to rid yourself of the annoyance until you can get to the car repair shop. This is a simple repair performed in emergencies.
Step 2 - A Longer Fix
Rather than repairing the headliner straight away, you might need to wait until you can go to town and get parts. One simple solution to this is to use a sewing kit, and just sew the material back together. You may need to stretch the thread back and forth between the tear, as there is little flexibility in the materials, but you should be able to weave enough of the parts back together to prevent it from flapping around. This is not a long-term repair, however, as the tear will eventually expand.
Step 3 - Fix the Tear
There are two ways in which you can fix the tear on your headliner permanently. The first is to simply take a piece of replacement fabric, and cut out the torn piece with a craft knife. You can then sew the replacement over the exposed upholstery, and this will give you enough material to make a good repair. It will not look very elegant, but most people don't spend a lot of time staring at the ceiling of their cars.
Step 4 - The Other Fix
Use the screwdriver to take down the piece of upholstery, and take off the loose piece of material. Using the glue, lay the torn pieces flat, and then fix them into position. You should glue the corners, and press these down until they stick. You can then move backward along the ceiling until the material is unwrinkled. Leave this to dry overnight, and then return the upholstery to the car. Screw back into position, and the tear should be completely repaired.