Grey tape is great stuff. For creating a castle out of cardboard boxes, there’s nothing better. But unfortunately there is another regular use for grey tape.
Entering a nursery one day, I noticed a skip with several rest mats on top, each sporting a border of grey tape. Inside I saw more mats in similar condition. On enquiring, I learned that this nursery’s rest mats often did not last one year before splitting along their heat-sealed edge. Heat-sealing is a great technology for making seams moisture-resistant. However if all the seams are heat-sealed, there is a problem: When a child plops down on a rest mat some of the air inside escapes, bursting a seam. To avoid this problem, we heat-seal the seams between our rest mat’s panels for moisture resistance, but we sew a tough binding round the edge so air can escape and to prevent wear and tear.
If I were a rest mat, I would rather fancy sporting grey stripes and retiring after twelve months. But nursery owners prefer Rest mats that last ten years. So make your children and staff happy, and save the grey tape for box castles.