When a shoelace is secured with a knot, the lace is crimped, or squashed. Primarily this is what stops the lace from coming undone. In effect, the lace is narrower inside the knot than it is on the loose end, and the loose end cannot make itself smaller and slide though the knot. Generally, a flat tubular lace will stay tied more easily than a round lace with a core because the flat lace can be more crimped within the knot. Most laces, however, are round and have core of cotton yarn, especially boot laces. For these to stay tied securely, the core on the inside of the lace must be soft and compressible. A secondary factor of laces coming undone is the knot itself slipping. This is due to a lack of friction. Cotton laces have a rough surface and will make a more reliable knot compared to polyester (the most common yarn used in shoelaces). In addition, a lace can be smooth or have a coarse surface, which will also affect performance. Finishing processes are available, including waxing and silicone treatments, which enhance friction and stop knot slippage. These are important design factors in the manufacture of hiking-boot laces.
Common bow Shoelaces are typically tied off at the top of the shoe using a simple
bow knot. Besides securing the shoe, this also takes up the length of shoelace exposed after tightening. The common bow consists of two half-knots tied one on top of the other, with the second half-knot looped in order to allow quick untying. When required, the knot can be readily loosened by pulling one or both of the loose ends. When tying the half-knots, a right-over-left half-knot followed by a left-over-right half-knot (or vice versa) forms a square or
reef knot, a fairly effective knot for the purpose of tying shoelaces. However, tying two consecutive right-over-left half-knots (or two consecutive left-over-right half-knots) forms the infamous
granny knot, which is much less secure. Most people who use it will find themselves regularly retying their shoelaces. If the loops lie across the shoe (left to right), the knot is probably a square knot. If they lie along the shoe (heel to toe), the knot is probably a granny knot.
Other more secure knots There are several more secure alternatives to the common shoelace bow, with names such as Turquoise Turtle Shoelace Knot, or ''Shoemaker's Knot'', Better Bow Shoelace Knot, Surgeon's Shoelace Knot, and Ian's Secure Shoelace Knot, or
double slip knot. One such knot has been patented in 1999 under the title "Shoelace tying system". These are all variations of the same concept of looping the top part of the knot twice instead of once, which results in a finished bow of almost identical appearance but with the laces wrapped twice around the middle. This double-wrap holds the shoelaces more securely tied while still allowing them to be untied with a (slightly firmer) pull on the loose end(s). Possibly the simplest, also neat and quite effective, is after tying a common bow to tie a
half-hitch with one or other loose end around its adjacent half bow, close to the knot; it is untied by pulling on the other (unhitched) free end.
Length The proper length of a shoelace, fitting it to a shoe, varies according to the type of lacing used, as well as the type of lace. However, at a rough reference the following guide can be used. == Shoe lacing ==