In addition to the way illustrated on our web site, I often use a similar method.

No pics, but here's a writted description. Basically begin by finding the middle of the garter, and place this on the outside of your leg, where you want the tie to be. Then cris-cross the garter around your leg, pulling it tight (but not turnoquet tight). Then simply tie the two ends together in an overhand knot. Pull tight, and then tuck the ends of the knot back and under the original (center) part of the garter, which will now serve to hold the knot in place.

I've worn them this way all day long and not experienced a bit of slippage. What's more, using this method I seem to be able to tie the garter so tight that I can barely slip my sgian dubh in my sock, yet it never feels uncomfortable or as if it is cutting off my circulation at all.