if you have flag hinges there is an Allen key underneath that you can turn to raise the slab.
steve

Hi there, you can alter the height of your PVC-u door by taking off the rubber caps on top of the hinges to reveal a Allen key bolt. You will need to turn each adjusting bolt two turns each until the door stops fouling the floor. However, you need to keep checking that the door still closes as the locking mechanism may start to foul.

Hope this helps

Depends on style of hinge if it's a laird type not really but if it's the type where you have bigger part of hinge on door itself then put either 4mm or 5mm alen key in bottom of the hinge the bit that's on the door and turn it till you see it lift you may need to adjust keeps on lock side if you move it to high but you should get about 6pm lift of hinges also you most do this to the 3 hinges

Most pvc doors you can adjust, there is a cover cap on the hinge that can be removed, this will reveal a screw. using a alum key turn the screw to lift or lower the door. Hope you find this helpful.
Kind regards
TRM.Builder.