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