Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a horror thriller written and directed Wes Craven, who also directed another movie with snakes, The Serpent and the Rainbow, along with A Nightmare on Elm Street, and Scream. In this one, the civilized middle class Carter family from Cleveland on their way to L.A. strand their car and trailer on a deserted road in the Mojave desert. They are discovered and attacked by a savage family of psychotic criminals who live up in the rocks like wild animals, drinking raw blood and killing whatever they can find to eat, including other people. The movie shows us that sometimes savages can become civilized and sometimes civilized people will act like savages to protect themselves.
Mrs. Carter has an obsession with rattlesnakes and quotes some ridiculous statistcs about rattlesnakes that she attributes to Marlin Perkins - "Marlin Perkins says rattlesnakes can reach lengths of 20 feet and can kill you in eight minutes. Or was it eight feet and 20 minutes?" When I heard that, I knew we were being set up to see a rattlesnake bite at some point in the movie. Later that night, two of the wild men break into the trailer, kill a woman, and steal her baby, planning to eat it later. The baby's father Doug rescues it with the help of Ruby, the sister of the wild man who kidnapped it, named Mars. Mars chases Doug Ruby and the baby. Doug runs into the rocks into a dead end where he drops his knife next to a rattlesnake. Mars sees a second snake and tells Doug "you got yourself trapped right where they breed, boy." Nothing else happens, but we are set up for what happens later. Ruby distracts Mars which allows Doug to get away from the rattlesnake. Mars and Doug start to fight. Ruby finds another rattlesnake, pins its head with a forked stick, then picks it up behind the head and runs with the snake toward Mars. She holds it to the back of his head where it bites him and he falls down in agony and gets savagely stabbed to death by Doug.
Despite the cliche of using a rattlesnake as a weapon, and the dumb idea that rattlesnakes collect together in one location when they breed (he should have said they were at a hibernation den) the way the snakes behaved and Ruby's handling of the snake was believable. And I know that everybody watching was cheering on Ruby and the snake against her psycho brother. The snakes are a combination of live rattlesnakes and either fakes or dead snakes. The snake Ruby picks up is either dead or a very good fake. The snake next to the knife is a black-tailed rattlesnake, not a common movie rattlesnake. The other is probably a western diamond-backed rattlesnake or maybe a red-diamond rattlesnake.