People have experimented with many different materials for bat gates, including mild steel rebar, angle iron, tubular rectangular steel, stainless steel, and mangalloy hardened steel.  The standard angle iron gate is far superior in strength-to-weight ratio, cost, availability, and ease of installation, but other materials may be used in certain situations.

 

Round bar gates, whether case-hardened or not, are extremely susceptible to bending and therefore entry by unauthorized persons. Additional vertical supports are required for round-bar gates, but they are not well tolerated by bats.

 

Stainless steel is expensive and difficult to work with, and should only be used where environmental conditions require it.

 

Rectangular bars are heavier than angle iron, a major factor if materials must be airlifted to the site. They also take up more of the available cross-section of the opening, thereby further restricting available flight space. However, special designs that reduce or eliminate the vertical columns may offset the difference.



The standard 4"x4"x⅜" angle with two 1½"x1½"x¼" stiffeners welded inside the apex allows vertical supports to be up to 10 feet apart, and provides maximum flight space in any gated area. Adding stiffeners will increase the weight, cost, and construction time.

 

Cable nets and gratings are used whenever airflow must be maintained but bat flight is not a major consideration.