What knots do you feel are essential? Which do you think are useless?

Personally, I've found these to be the ones to know:

Bowline (and sheet bend)
Cleat Hitch
Reefing (square)
Clove Hitch (for fenders)
Figure 8 (for stoppers)

That's about all I use. Granted, I don't have my own boat to rig, so there are plenty that I haven't had to deal with I'm sure.

Chris,

I think you pretty much nailed it. With what you have listed you can do what needs to be done. Add to your list: how to coil a line and how to heave a line and your set

I agree with your list and would add one more that I use all the time. It's the taut line hitch (modified rolling hitch). It's an adjustable knot that will slide along to easily tighten a line or loosen it. I often think of it as a tent guy line hitch.

www.animatedknots.com/rollinghitchboating/index.php

What's the best knot for tying around a piling? I've run into some very awkward arrangements at some less than savory marinas where cleats are non-existent and the only thing you can find is a piling or something cemented into the ground. Typically I've fashioned a heavily wrapped hitch around it and just hoped for the best. I think the answer is a rolling hitch as you mentioned todd, but opinions are largely varied out there.

I am surprised that you didn't include the Round Turn & Two Half Hitches. I use that to tie up to the pier if there aren't cleats.

Chris wrote:
What's the best knot for tying around a piling? I've run into some very awkward arrangements at some less than savory marinas where cleats are non-existent and the only thing you can find is a piling or something cemented into the ground. Typically I've fashioned a heavily wrapped hitch around it and just hoped for the best. I think the answer is a rolling hitch as you mentioned todd, but opinions are largely varied out there.

I've done a bowline around the whatever and adjusted at the cleats on my boat. That doesn't use up too much of my dockline on the big diameter whatever ashore.

Which reminds me, I like to use a dock board in those situations as well. I use a 2 x 6 about 36" long. It has 2 holes, each drilled from edge to edge near either end with a piece of 3/8" or better line run through each hole, each piece of line has a knot at the end. I then hang the board between my fenders and the nasty wall (tied to my boat of course).

Pablo wrote:
I am surprised that you didn't include the Round Turn & Two Half Hitches. I use that to tie up to the pier if there aren't cleats.

That's a really good knot on a ring too.

If you have easy access to the top of the piling you're tying to, I like the clove hitch. If your securing someone elses boat and you're on the receiving end of the line and conditions are nasty just a couple of wraps to get things secured is the order of the day. Finish with a couple of half hitches. note, Always follow the skippers orders. Never secure a line until he gives the order.

Todd's fender board is a great idea. There used to be a product on the makket that acted as bumpers at the ends of the board to rest against the hull. There were two sizes. 2x4 and 2x6. Haven't seen them in years.

For securing an object, such a a dingy on car tops, I love the truckers hitch. Negating friction, you have a 2 to 1 purches to tighten the line.