If your shifting is off and you need to make an adjustment but do not have a bike stand. Try a door knob.
I apologize for the poor picture quality.
Step 1: Hang the rack on the doorknob
Hook the bike rack frame over the doorknob. Some racks will have a different configuration. If your rack wont hang on your door knob, try zip tying it.
Note: it is best to have the chain side facing towards you to make adjustments easier. My pics show the opposite.
Step 2: Angle bike to allow pedal clearance
Face the handlebars away from the wall and angle the bike to allow the pedals to rotate without touching the wall.
Step 3: Now adjust your derailers
You are ready to adjust your bike now.