Run it to the edge
A white stone sits on the first line with your stone already pressed against one side: two liberties, and the edge has locked off the third direction. A first-line ladder is a chase with a fixed script — atari from the second line, the runner crawls along the edge, atari again, until the corner stops the script. The edge is what makes it work: a first-line runner picks up one liberty per move while a centre runner would pick up three, so the count runs out. Black to play: start the ladder — atari the white stone.