If, for example, someone has been bit by a dog in the thigh area (including lower or slightly upper regions), he/she may have suffered serious damage to the femoral artery. In this case,keeping in mind that this artery arises from external iliac artery → which is aorta's second largest internal branch ← this would mean that, if not stopped,the bleeding may ensue with death in max. 30-40 minutes!
So,you must stop the bleeding at once!
Simply look carefully for the person's inguinal ligament → it's found at the imaginary crossing of its halves, where you should be able to see the artery's pulsations (the place,roughly said, is where the leg attaches to the hip).
Compress with your thumb(or find a suitable substitute) upon it,in order to minimize bleeding.That's it!
Basic simple maneuver that saves lives...