If you have more then one set of runners, you’ll have to shim them or realign your chocks every time you change runners. I have an easy way to shim runners using a rifle scope and a spare chock (you can use one from your plank if they aren’t epoxied on). The first thing you have to do is make a fixture for your scope. The drawing below is for the one I use.

You can use any rifle scope, but a .22 cal scope is far cheaper (a decent one can be gotten for under $25) and is easy to attach since they have a built in clamping mount.

The following is the procedure I use:

1. Take your chock and mount it on a piece of 2x6.
2. Clamp the 2x6 to a sturdy surface such as a porch railing.
3. Next make a target with a vertical and horizontal crosshair and place it about 50ft in front of the chock.
4. Take a runner and mount it in the chock. Make sure you only tighten the runner bolt as tight as you would when sailing.
5. Line up the center of the dowels on the fixture with the runners edge and press down. Use the notches made as the guides.
6. Roughly aim the runner at the target. Place the scope directly over the runner bolt hole. Rotate the chock until the vertical line is lined up perfectly with the cross hair in the scope (the horizontal line will aid in keeping the scope exactly vertical). Clamp the 2x6 down so it won’t move.
7. Remove the runner and mount the other one from the set in the chock. Use the scope to see how it lines up compared to its mate. Using shim tape on what will be the inboard side of the runner, shim it until it lines up perfectly on the vertical line. You now have a set of parallel runners.
8. Do this with each set of runners you have. Now you’ll be able to change runners without having to align your chocks.

You can make your own shim tape. Buy light weight fiber glass from a hobby shop, saturate it with superglue, squeegee out the excess, spray it with an accelerator like Insta-Set and cut the sheet into strips. The strips can be superglued on the runners. If they are too thick, just sand them to the proper thickness.

The scope and fixture has another use. I use mine to check the trueness of a runner’s edge when sharpening. Just slide it down the runner’s edge to see if there are any lateral deviations.

Using a rifle scope to shim runners isn’t as high tech or as much fun as a laser, but it’s cheaper, easier to set up and works quite well.