Another method of achieving constriction of the supplying artery is the use of a tourniquet - a tightly tied band which goes around a limb to restrict blood flow. Tourniquets are routinely used in order to bring veins to the surface for cannulation, although their use in emergency medicine is more limited. The use of the tourniquet is restricted in most countries to professionals such as physicians and paramedics, as this is often considered beyond the reach of first aid and those acting in good faith as a good samaritan.