ENTRANCE DOOR HORIZONTAL ADJUSTMENTS
Entrance doors often warp from season to season and are hard to close in the winter and rattle in the summer. This requires moving the strike plate horizontally -- but the good fit changes from season to season. Don't adjust it at all -- but rather follow this link for the automatically self-adjusting door latch for warped doors.
INSIDE DOOR VERTICAL ADJUSTMENTS
When a door latch plate is just barely out of line vertically, catching the door sometimes but not all the time, you can make a very quick and easy adjustment. Simply take a knife and score the wood below or above the plate, in the direction that the plate needs to move to catch the tongue properly. Then remove the plate and clean out the little shelf of wood.
Fill the screw holes with toothpicks, preferably round ones made of hardwood. This works best if the toothpicks are actually harder than the wood of the door itself. When you screw the latch plate back on, simply place the screw point in the crack between the toothpick and the old screw hole. The hardwood toothpick will force the screw into the soft wood of the door, shifting the screw about 1/8th of an inch. Often that is exactly what you need. The whole job can be done with a pocket knife and a screwdriver. Any serious home repair person always carries tooth picks with them. For a door hinge that requires more holding power, put some glue in the hole before inserting the toothpick.
EUROPEAN CABINET HINGES
How do you adjust those kitchen and bathroom doors that have European hidden hinges? Each hinge has two adjustments. The screw adjustment in the first photo will push the hinge in or out from the wall of the cabinet, perpendicular to the mounting bracket that is inside the door. This will cause the handle side of the door to rise up or drop down when in the closed position. The screw is a bit counter-intuitive in that driving the screw in pushes the door out. Playing with all four hinges, just a little on each one should get the doors to look perfectly lined up and the joint between two doors to be parallel. Drawing both screws on one side out will pull the door away from the other door, enlarging the space between them so they do not hit as they open and close.
The screw further back in the second photo releases the hinge from a track, allowing you to slide the entire hinge into the cabinet or away from the cabinet. Again, play with all four hinges until the doors close evenly. This adjustment is not actually a screw adjustment, the screw just tightens down on the rack arrangement, and so you have a limited number of discrete positions available.
ADJUSTING THE SPEED OF DOOR CLOSERS
The last photo shows the adjustment screw for an automatic door closer. This one works on a spring pressing against a cylinder of air and the screw lets the air out faster or slower. Hydraulic door closers, used for heavier doors, work on the same principle, allowing the oil to flow from one chamber to another more or less rapidly. Remember that the screen door closer needs to snap shut the last couple of inches or it will not engage the latch, so if you set it to move too slowly, it may never close. The hydraulic door closers often have a separate screw adjustment for the last few inches.