a tourniquet works bye constricting the veins or artrery in the limb before the wound thus stemming the bleeding , this is a very dangerous practice and can cause cellular dammage the way i was tought to do this was to squueeze the the area of the limb above the wound with my hands or even standing on it till the blood is stoped thus only restricting blood flow to one part of the limb and not the whole thing
Tourniquets are a somewhat discredited way of treating injuries now as, by cutting off or restricting the flow of blood to areas below the wound, they can cause more harm than good.