Abstract: A sliding gate line blind for preventing fluids from traveling downstream from the blind including a body for connection to a pipeline, the body being open to the atmosphere and having an inner portion and an outer portion, the body having an entrance passage and an exit passage, an axially expanding gate assembly slidably received in the body for selectively sealing and opening the pipeline, the expanding gate assembly including two planar surfaces having openings therein for alignment with the entrance passage and the exit passage to permit flow through the pipeline and sealing surfaces for alignment with the entrance passage and exit passage to stop flow through downstream from the sliding gate line blind, and an actuator for moving the expanding gate assembly within the body to selectively seal and open the pipeline.