This spring I was on a short camping trip to Svalbard, 78 deg. north. Due to the danger of polar bears it is mandatory to take necessary precautions to avoid injury from attacks (that is injury to both bears and people). One of several necessary precaution is to set up tripwires around the camp. I made these that can be attached to the skis with duct tape. Setting up tripwires requires knowledge on the subject as they are useless if set up wrong, and very dangerous, no kidding.

THESE DO NOT PROVIDE ANY FORM OF SAFETY. THEY MAY ALSO CAUSE FIRES AND SERIOUS INJURY EVEN IF USED AS INTENDED.
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These should be printed in high density as this is not where you would want to save on plastic.

Use non-elastic multi-filament fishing line for the actual trip wire.

Use stainless steel shackles in the corner holders to run the fishing line through (you could probably strap the shackles directly to the skis without the holders).

Use a partly unthreaded screw in the hole going trough the holder above the hole for the spool axle to lock the spool.

If you can't figure out the rest you probably should go for some commercial product with a manual. Setting up tripwires requires knowledge on the subject as they are useless if set up wrong, and very dangerous, no kidding.

THESE DO NOT PROVIDE ANY FORM OF SAFETY. THEY MAY ALSO CAUSE FIRES AND SERIOUS INJURY EVEN IF USED AS INTENDED.