This happened during my first few weeks of new employment at a sheet metal warehouse. I was assigned to bring 14ft trays down to be cut and shaped. These trays we're equally as high, near max of the forklift. I did it and was backing and turning due to the limited amount of space. I proceeded to drive through the bay doors but misjudged the height and bam! I hit it at the top, the whole metal building shook and my I lost all strength and words. I just closed my eyes and expected the building to fall. The office staff came out and the other warehouse workers gathered and simply laughed. I backed up and lowered it. I stepped out to calm down. When I came back, I went to inspect the damage. Apparently this was a common occurrence because it was deeply scared and dented everywhere.