loosen the harness. Once adjusted, some flexibility is still allowed by positioning the buckle, which can change the effective length of the waist strap depending on where it is secured. The harness webbing can be replaced at home with no special tools when the webbing wears through or is damaged, and other components can be easily replaced. This makes this style of harness very economical over the long term. Harness accessories D-rings or a functional equivalent are usually fitted to the waistbelt, shoulder straps and crotch strap to secure stage cylinders, additional equipment, and clipping off demand valves, light heads, and submersible pressure gauges which are not currently being used. The number and position of these D-rings can be adjusted by the user, but there are a few positions which have become fairly standard. Left and right shoulder strap at roughly the height of the collar bone in front. Left hip just forward of the backplate. Crotch strap at the back and front. The front one is used for a tow-line when scootering Weight holders are available for integrated weight systems which can be slid over the waist belt. Canister lights can be carried on the waist belt. The standard position is on the right side. A small diver's knife or cutting tool is commonly carried on the left side alongside the buckle. Backup lights are generally clipped to the shoulder D-rings and held against the shoulder straps by rubber bands cut from bicycle inner tubes. Other methods are possible, but the inner tubes work and are easily replaced when they wear out. Many variations to this basic harness are used, and these may include: Differing number or positioning of D-rings. Shoulder straps that cross behind the diver's neck. No crotch strap. An additional chest strap, which crosses the diver's sternum. For divers who find it difficult to get the harness on or off, a buckle may be fitted to one or both of the shoulder straps. The left shoulder strap is particularly convenient because this is the side where most dry suits have the auto-dump valve, which tends to snag on the harness. Neoprene padding tubes are used over the shoulder straps by some divers for comfort. Some manufacturers offer alternative harnesses, often marketed as “deluxe” options, which may include the above variations. Omitting the buoyancy bladder reduces the setup to a plain backpack harness if the breathing set