A Simple Scaffold
Measure the distance from the bottom of the stairs to the step you'll be placing the catwalk or plank. Add about two feet to the length so you can butt it up against the rise of the step and extend between 6 inches and a foot beyond the ladder.
Open a step ladder at the base of the steps
Slide the board through the middle of the ladder to rest on a step and rung of the ladder and rest the other end on the step. Make certain that it is level.
A Scaffold Made from an Articulating Ladder and a Step Ladder
Open a step ladder at the top of the stairs. In this example we will use a 6-foot ladder.
Set a 12-foot articulating ladder at the base of the steps by putting the base feet on the main floor and adjusting the ladder so that a shorter end rests several steps up. An articulating ladder is one that bends and folds in several directions.
Extend a catwalk or plank between the step ladder and the articulating ladder.
Rent mini scaffolding, which is just right for stairs. If there will be many uses, it may be worth considering a purchase. The scaffolding is a platform that has two braces attached and two end frames.
Connect a platform to the end frame at the base of the steps at the appropriate height. Secure the braces
Decide which step is the right height for the opposite end and put the other end frame on that step, connecting the platform and securing the braces. You are now ready to begin.