In 2003 I wrote an article for JLC about installing fiber cement siding, and at the time we used a jig from Malco for holding one end of the siding. It worked ok, but not as well as we would have liked. We later switched to PacTool’s Gecko Gauges and have been using them for quite a few years; they have done an outstanding job. There are six different models, each for use with particular types and sizes of siding. We have the ones for 5/16-inch fiber cement and 3/8-inch LP Smart Siding. Trust me; they can’t be used interchangeably so if you use more than one kind of siding buy more than one set of gauges.
Gecko Gauges are adjustable in 1/4-inch increments for various siding reveals. The ones we use can be set between 4 and 9 inches. They won’t scratch the siding, which is important if you install prefinished material.
The gauge is installed by slipping the tapered steel blade (on the bottom back side of the gauge) behind the lower edge of the last piece of siding and pushing up on the handle. This creates a friction fit that holds the gauge in place while it supports the next piece of siding. If you use two gauges, you can install and nail siding without doing layout.
The bodies of our gauges are made from tough plastic—which makes them more resistant to wear and damage than the wooden gauges we used to make. A couple of models (not the ones we have) are made from aluminum.
In my opinion these gauges are a must for siding crews. They speed up the work and I find that I’m way less tired after installing siding myself (the material is supported so I’m not using muscle to hold it in position for nailing).
Gecko Gauges are made in the USA and can be found online or at the lumberyard for about $60 a pair.