You don't need to spend money on a Tiller-Tamer to hold your sailboat's tiller in place if you need to let go a short time when underway. Two very inexpensive methods are available for do-it-yourselfers.
Larger sailboats, especially those with long or full keels, will often stay on course for a short time if you need to release the wheel, and most wheel-steered boats have a "wheel brake" to temporarily lock the wheel in place. But with a smaller sailboat, especially one with a centerboard rather than a longer fixed keel, the boat usually loses course immediately if you have to release the tiller. It may head up into the wind and stall or be blown off the wind and out of control.
These methods "tame" your tiller by holding it in place if you must let go for a short time.
Shock Cord Tiller Method
This is my own preferred method, which served me well for years. It's cheap and simple and works well. First, check your boat for attachment points on both sides of the cockpit at the level of the forward half of the tiller. Some boat owners install small U-bolts, but anything you can tie or wrap a cord around works fine.
Measure the distance between these points and buy a length of shock cord (like a bungee cord) at your hardware store or chandlery. Attach one end on one side, pull it to the tiller and wrap it twice around the tiller, and then attach it to the other side. The first time, take a few minutes to adjust the tension of the cord so that it holds the tiller in place but is not so bar-tight that you can't adjust it: move the tiller, rotate the wraps on the tiller, and release, and the tiller should stay in the new position.
There are two advantages of using shock cord. First, if the boat slides off course with the tiller in position, you don't have to release the cord to make a correction; simply move the tiller to get back on course, and then let it spring back to its original position. You can even tack without releasing the cord, and let it then hold the tiller in place while you bring in the jib sheet. Second, if a wave or other force pushes the rudder strongly, the shock cord has some give and absorbs some of the force on the rudder-tiller joint, easing the strain and preventing breaking something.
Dock Line Tiller Method
This is similar to the shock cord method, but you can use an existing dockline or other short length of rope. With this method, it is better to use attachment points parallel to the aft half of the tiller (even stern cleats), so that the lines can be angled forward from the sides.
Again, tie one side first, then bring the line forward to the tiller - not directly across the cockpit in a straight line. Wrap it twice around the tiller and then back at the same angle to the other side.
Here's the trick for using this method. When you slide the wraps forward along the tiller, both sides are tightened to lock down the tiller. But you can easily move the tiller again, without having to remove the line, by sliding the wraps aft, putting as much slack in the line as you need to make a turn.
Experiment a bit to get the best attachment points for your boat. Ideally you can set this up so it's always connected and ready to use but instantly slides back and out of your way. Experiment also with the number of wraps around the tiller. You need enough wraps (two, three, or four) to provide enough friction so that the wraps do not slip and let the tiller move, but not so much that it's hard to release the tiller by sliding the wraps aft on the tiller to loosen them.
Voila! With either method, you just save about thirty bucks!
The Tiller-Tamer is a commercial product that functions in a similar way with a cord from one side of the cockpit to the other (at 90 degrees, usually at the aft corners) through a special mechanism mounted on the tiller. This mechanism has an adjustment pressure knob allowing a range of tension between complete tiller locking to free tiller movement. I have used this device and find it works very well.
Its disadvantage, in addition to the cost, is that the mechanism is mounted on the tiller and remains there. The attachment points also must be at 90 degrees, often requiring hardware mounting. The line too, although it can be removed, is more difficult to thread back through the mechanism. So most people always leave the device in place rather than just using it as needed, as you can with the previous two methods. Some sailors feel it is in the way and the mechanism an unattractive appendage to the smooth wood of the tiller.