Securing a glider to the ground is important, and need not be complicated. The midshipman’s hitch (Ashley’s Book of Knots #1855) is a variation on the taut-line or rolling hitch knot and is useful for tying down aircraft. It is adjustable, yet if properly tied will not slip under tension. The knot is easily tied while under tension, and easily untied when tension is removed. For aircraft, I recommend tying two midshipman’s hitches, with the second holding tension on the first.

I like to tie the first knot fairly close (within six inches) of the tie down on the aircraft. I will then tie another midshipman’s knot about half-way or more down the standing part. Adding “bows” or other variations to make untying the knot easier is often counter-productive. These invariably come unwound under tension and cause the knot to loosen. It's not necessary either... just use one hand to remove the tension, and you can easily untie the knot with the other!