What is a metal bar that runs between the beams of a wooden ladder called?

A metal bar that runs between the beams of a wooden ladder is called a tie rod. Tie rods are structural components used to provide additional strength and support, ensuring that the ladder maintains its shape and integrity under load. They help to prevent the beams from spreading apart or collapsing, especially when weight is applied during use. This design is essential for maintaining safety and stability while climbing or working from the ladder.

The other options refer to different types of materials or components. A spring bar is typically not associated with ladders but may be used in other contraptions or mechanisms for tension. Rebar is used primarily in reinforced concrete construction to provide tensile strength; it has no application related to wooden ladders. A basket arch is a design element often found in architectural structures, but it does not pertain to the functioning or construction of ladders. Understanding the role of tie rods in maintaining the structural integrity of wooden ladders highlights the importance of recognizing various components in firefighting and rescue equipment.