This is probably the most common repair we do. Nearly every car/truck on the road today has what we call a 'bonded' headliner. The term comes from the construction of the headliner fabric - a layer of colored fabric which is bonded to a 1/4 inch thick layer of foam rubber by the manufacturer. The layer of foam is the culprit when it comes to failure - as it degrades over time, from heat, humidity, vibration - the fabric outer layer loses it's bond and separates, resulting in a sag. Typically the sag starts where the headliner board (to which the bonded headliner is attached) forms a concave shape - the fabric has been stretched to conform and the combo of age and the inherent pressure the fabric has been put under cause the separation. Once that has happen, it's game over. You cannot re-glue that section, as the rotted foam underneath will simply peel off another layer and sag right back down. Quick fixes (you didn't hear me say this) include strategically placed thumb tacks or staples placed in the sagging area to physically hold the fabric to the board and minimize the flopping around of the fabric, which just pulls more of it away from the foam. When you can't stand it any longer - come on by, we can match the correct color and get you a new bonded headliner in short order!