I have several pairs of shoes with shoelaces, and the laces are always coming undone. To solve this, I tie double knots in most cases. The difficulty is that, when untying them, the knots often get tangled; and it’s a real hassle (involving skewers, or my wife’s superior manual dexterity) to undo the tangles. This seems particular likely to occur when I am going through an airport security check.
My pair of New Balance walking shoes came with laces that look like a row of peapods strung together. A single knot always suffices to prevent them from coming undone. This technical improvement saves me time tying and re-tying my shoes, it improves the flow of traffic at security stations and it even reduces the risk of a shoelace breaking. I’m surprised it isn’t more widespread-it could represent an important outward tilt in the economy’s production possibility frontier.