Group, I have been following the string regarding marking the waterline, and have a few things to add. I use lasers in construction on an almost daily basis, and I believe that the laser idea is a great one provided that, as Connie says, that the laser and the entire desired waterline (both sides) of the boat are on the same plane. I have several lasers: a 'Robolaser', a more sophisticated 'David White' rotating laser, and a simple torpedo level with integrated laser. The former two are self leveling--which is to say that the laser mechanism inside the case is a pendulum, and will always cast a line/dot that is on a level plane. The latter has to be leveled via two vials. Any of these, when mounted on my height adjustable tripod, is capable of a moving dot or line (manual in the case of the torpedo laser) that will give you a virtual slice through a plane. The trick is to get the boat's desired waterline on the same plane as the laser. Might I suggest the following method for waterline marking? My boat (was still 'new' when I picked it up) had three grease pencil markings on the hull--one on either side aft, and one at the bow. When I first launched, these marks lined up more or less perfectly with the actual waterline. I would propose that you load the boat/distribute your anticipated gear, engine, etc. (perhaps humans too), and then with a grease pencil, mark the actual waterline with three marks per side from the dock (transom/hull intersection, amidships below shrouds, and bow). These marks will provide you the means of confirming that the laser is in fact on the same plane (fore to aft, and port to starboard). If the laser is leveled, but the boat is not, or if the waterline is not too be level on account of the way the boat sits in the water do to loading, etc., the adjustment can be made by raising or lowering the tongue, and/or by jacking one side of the trailer. You may have to raise or lower the level's elevation as the adjustments are made, but it would be best to keep it level in all directions (consistent level plane) and adjust the boat accordingly. You know that you have it right when the laser dot or line exactly hits all of the marks on the hull (both sides). Eventually, you will need to move the laser to the opposite side of the hull for marking the actual line, but while confirming/adjusting the boat relative to the laser plane, try setting up the laser so that the dot/line plane is just below the hull. You can then use a tape measure (held plumb from the marks on the hull down to the laser dot/line) to verify all six marks without having to move the laser and recalibrate. When you do move the laser from side to side, make three or more reference marks on opposing walls (or some stationary object other than the boat) to use for recalibrating your laser plane. This may sound complicated, but in fact is very easy (especially with the Stabila level tripod that allows for vertical changes in the laser plane without affecting level). Many of the less expensive lasers out there will fi t a standard photo tripod. I know the laser, when set up properly, will work with rounded objects. We have used one to set up mounts for a huge above ground water tank. Good luck! Scott Grometer, M15 #478 'bebe'