Once the nails are all set, they’ll start installing the roofing around the perimeter of the house. This includes attaching the shingles to posts on each side. In some cases, they’ll have to run these up and down a number of flights of stairs. They may also have to use a ladder to reach areas that aren’t shingled down. At the very least, the shingles will have to be installed in such a way so that they line up perfectly.