This how to video tutorial demonstrates how to tie a Turk's knot for sailing. Follow along with the step by step process and the directions below to learn how to tie the Turk's knot.
Make 3 turns and follow this sequence: u-o-u-o-u, then around to the right of the standing end, o-u-o-u-o, then back o-uu-oo-uu-oo-u, then to the right of the standing end u-oo-uu-oo-uu, and from there you do an under and over working your way all the way back to the standing end.
From there you straighten everything out, then double/triple or however many passes you want to make(the 20 feet of 550 paracord I used is enough for 3 passes on a 2C Maglite).
Then you'll gradually work the slack out, tighten it up, and work any twist out of the cord as you go.
You can use various sizes and types of cordage to make these types of knots and apply the to various things like: flashlights, walking/hiking staffs, oars, paddles, lamp posts, knife handles, motorcycle/bike grips, pens, letter openers, railings, pot handles, etc.
After you've made a few, you start looking for things to add a Turk's Head to. They're an addictive puzzle of ropework.