Aluminum formwork is made from a lightweight metal that is easy to transport, set up, tear down, and clean. Other types of formwork exist as well; steel and plywood are the most commonly used types of forms. Aluminum formwork is advantageous, however, because it is durable but lightweight and easy to set up. Plywood can, however, be susceptible to water damage and may also warp; steel can be heavy, difficult to position, and difficult to store and transport. Aluminum formwork avoids these pitfalls, though it has drawbacks of its own. Aluminum is a fairly rigid, brittle metal that is prone to cracking when bent. Steel is more resistant to such types of damage, but tends to be more expensive than steel, however. Like other types of formwork, aluminum formwork can be purchased or rented. It is possible to rent forms for small to medium projects; if the user will be doing concrete projects frequently, it is best to buy forms that can be reused. Aluminum is a good choice because it will generally be less expensive than other types of formwork, is easily stored and transported, and can be easily cleaned between uses to ensure the panels can be used for future projects. The thickness of the aluminum will generally dictate which projects the forms will be most appropriate for.