My furnace mounted AprilAir humidifier needs regular adjustment to get a proper water flow. I grew tired of yanking off the entire cover panel every time, so I created a hinged access panel just to see and touch the water level.

A piece of stove wire serves as the hinge pin. I cut out a hole in the humidifer, then glued the removed piece onto my hinge, and used that as a guide for mounting the hinge flap in the right space, and it adds some heft to keep the hinge flap down.