The guardrail face is the length of the guardrail extending from the end terminal alongside the road. Its function is always to redirect the vehicle back onto the roadway. The end terminal is the starting point of the guardrail and is commonly designed to manage the energy of an impact. The end terminal functions in two ways.  When hit head-on, the impact head slides down the guardrail flattening, or “extruding,” the guardrail and redirecting the guardrail away from the vehicle until the vehicle’s impact energy is dissipated and the vehicle has decelerated to a stop. When hit at an angle, the impact head may partially extrude the guardrail and then "gate" out of the way allowing the vehicle to pass behind the guardrail.