Ski Swap.

1. Approach a box or wide rail straight-on at a slow-to-medium speed (just fast enough not to stall), and settle into a stable 50-50 with both skis flat on their bases.

   Keep your eyes on the exit end of the rail, not the lip in front of you.

2. Near the middle of the rail, get ready to pop.

   Bend your knees and sink your hips slightly, keeping your upper body stacked over your pelvis rather than leaning. Having your weight centered directly over the rail is what lets you jump off such a narrow surface.

3. Quickly extend those bent knees and push straight down through the whole sole of both feet.

   Unlike snow, a rail gives no rebound, so the lift comes only from your own leg extension. Pop straight up and even on both feet — drift forward or back and your skis come off the rail.

4. As you pop, lead the rotation with your eyes and shoulders first, turning them toward where you want to go (180 degrees around, facing back).

   Let it travel eyes → shoulders → hips → skis, so the lower body gets pulled around naturally. Keep your arms and legs close to your body; the more compact you are, the less spin you need to hit a clean 180.

5. Once your face catches the new direction (the exit), stop the rotation.

   Learn the feel of a half-turn that leaves both skis lined up parallel with the rail. Over-rotate and the skis land crossed and slip off, so think "stop at 180."

6. Land switch (riding backward), setting both ski bases flat back onto the rail and bending your knees to absorb it.

   Don't tip onto an edge — keep the bases flat or they'll catch. Continue the slide in switch.

7. At the end of the rail, either ride off switch or pop another 180 at the exit to come back to forward.

   On the snow landing, bend both knees deeply and absorb through the full soles of your feet.

You can pin your own clip to the tricks you've landed (My Video).