How to Make a Low-Tech Perimeter Alarm Step 1: Place the Alarm. Tie together at least a few aluminum cans with a short length of paracord or wire/fishing line. ... Step 2: Tie Another Loop. Use more paracord to make a second loop below your cans. ... Step 3: Make the Trigger. ... Step 4: Create Your Perimeter. ... Step 5: Set the Alarm. Aug 20, 2020