The laser pointer is zip-tied to the top of the unit. Both of these units have withstood severe caving environments, although I am careful not to immurse them. As mentioned above, I have also expirimented with alternative distance measuring devices. The unit in my drybox above is by sonin. This system works well outdoors, but in caves, it leaves a bit to be desired.
Any obstructions cause erronius readings.
This can be maddening. One nice thing is that the master unit will fuction alone for distances of 60 feet, so its great for ceiling heights, and togather they work great for measuring pits. In general, however, they are not very useful- buy a good fiberglass tape instead. In closing, I would like to encourage you to investigate future technologies as their prices come down. There are devices available that will do all of our survey duties in one shot, they are just prohibitively expensive.