Searching for a ladders? Here's some info to help you find the right one. For many tasks, the rigid ladder is the type often used. Rigid ladders have many kinds - fixed, extension, step, platform step, and roof. The fixed ladder is the most basic, and has no moving parts. Extension ladders are composed to two ladders where one can retract into the other for easy storage. The ones that form an inverted V are called step ladders. If you need space to place things like paint cans, you might need a platform ladder, which has a platform at the top. Ladders that have hooks to firmly set them locked on the roof are called roof ladders. The preferred material for many ladders, except those used in electrical work is aluminium.