Leaf springs are positioned behind the wheel -- you can't see them clearly when they're attached unless you crawl under the trailer -- so the wheel needs to be taken off completely before installation begins. Once the wheel is off, you should notice a pair of hangers on either side of the axle. The hangars are usually small, extended pieces of metal with holes that hang down from the frame of the trailer. Between the holes of these hangers is where you line up the eyes of a leaf spring, securing them with the proper hardware. If the leaf spring is a double-eye, one hanger will have a shackle link.
Once the leaf springs are bolted into the hangers, the next step is to install a pair of U-bolts, two horseshoe-shaped metal rods. The leaf springs can be overslung (placed over the axle) or underslung (placed under the axle). Either way, the U-bolts fit around the axle and secure to a metal plate that rests against the leaf springs. The purpose of the U-bolts is to keep the leaf springs flush against the axle so they take the weight of the cargo and don't move around too much during driving.
It's always important to check leaf springs and their accessories for wear -- a worn or cracked leaf spring can cause untold damage to a trailer and its contents. When taking leaf springs off, it's a good idea to check the shackle links for wear. A round ring of wear that matches the shape of the nut is OK, but once the shape becomes an oval, it's time to replace the shackle link. Proper care of leaf springs will ensure a safe ride while towing by keeping the trailer's wheels on the ground and its cargo in place.
For lots more information on towing and towing accessories, see the next page.