The easiest way to adjust your oarlock/gate height is to use spacer split washers, but boy are they fiddly to remove.
Faster Masters Rowing designed the Spacer Placer Tool which easily pushes out the washer. The tool has a finger hole so you can control the pressure and long prongs which allow you to press on the washer from a distance. You can add your own lanyard so the tool won't drop into the water when you make an adjustment while out rowing. Fits all split washers.