Compared to most automotive technology currently available, leaf springs don't look too fancy. They're simply long and narrow plates attached to the frame of a trailer that rest above or below the trailer's axle. Slightly curved, they look a little like a metal bow from an archery set, except without the string.
Leaf springs come in several different varieties. There are monoleaf springs, or single-leaf springs, that consist of simply one plate of spring steel. These are usually thick in the middle and taper out toward the end, and they don't typically offer too much strength and suspension for towed vehicles. Drivers looking to tow heavier loads typically use multileaf springs, which consist of several leaf springs of varying length stacked on top of each other. The shorter the leaf spring, the closer to the bottom it will be, giving it the same semielliptical shape a single leaf spring gets from being thicker in the middle.
Leaf springs also have different ends, depending on where they're connected to the frame. On double-eye leaf springs, the top plate -- and therefore the longest -- has both ends curved into a circle. The ends make two holes, which you can bolt to the bottom of a trailer's frame. Open-eye leaf springs have only one "eye," or open hole. The other end of an open eye leaf spring can be a hook end or a flat end.
Properly installing leaf springs will ensure the best suspension for your tow vehicle; read about leaf spring installation on the next page.