I recently installed a lot of cabinets with the help of some simple plywood boxes. As shown in the drawing, I made the boxes out of scrap pieces of 3/4-in. plywood. Their dimensions correspond to the typical counter-to-overhead-cabinet heights.
While the boxes make it easy for one person to position overhead cabinets, they also have some other uses. When spanned with a plank they make a sturdy platform for working on door casings and crown moldings. Their cutout handles turn them into convenient containers for carrying tools and materials. Finally, they make handy stools at lunchtime.
Dan Jensen, Portland, OR