If you need a ladder for a particular task, you might want to know more about Ladders in general. This might help in your choosing the right ladder for the job. The all-around ladder is the rigid ladder, and it's often used for many tasks. Rigid ladders come in many varieties, from the fixed to the roof ladders. The fixed ladder is the most plain of these and has no moving parts. Extension ladders are composed of two ladders where one nests in the other for easy storage. The ones that form an inverted V are called step ladders. The one with a platform is of course called the platform step ladder. Roof ladders have hooks that set them firmly hooked on the roof. The preferred material for many ladders, except those used in electrical work is aluminium.