A boom hitch is a relatively easy knot to tie, and is quite useful if you need to attach a rope to a fixed object. Useful applications of the boom hitch include securing a tent line to a tree branch, securing a sail boom, or even tying a horse to a fence by his reigns.
To Tie a Boom Hitch Knot:
Start by bringing the working end of the rope over the top of the hitching post.
Bring the end of the rope under the post and cross it over the top from right to left. This traps the first loop of the rope under the new one.
Once again, bring the end of the rope under the post, and back over the top again. This time, cross over the top towards the right, and lay the working end of the rope between the loop you just made and the loop made in step 1.
Continue the pattern established so far by bringing the rope under the bottom, then over the top, crossing over from right to left. At this point, you should start to see the rope weave itself into a sort of web across the hitching post. This weave is where the boom hitch gets its strength.
Take what is left of the working end of the rope and loop it around on itself to make a loop. Feed that loop under the the loop of rope you made in step 2. Pull at both ends of the rope and the knot should tighten up well. To untie the knot, simply pull the loop free by the untied end of the rope, and unwind it from the hitching post.