A Vernier height gauge is a caliper on a sliding scale attached to a base block so that the jaws can make accurate measurements over or under surfaces, and it is read by subtracting the height of the lower caliper from the height of the higher with notation at every point to make comparison easy. These gauges are useful in many construction and measurement tasks.
Once the gauge's base plate is level it can be used as an ordinary ruler by virtue of the height notations along its length or as a set of calipers. Its jaws are adjustable and in sturdier models they are also serviceable as clamps. This makes the tool a tremendously useful one in precision construction projects, especially projects that necessitate the use of delicate wood like balsa.
These gauges are most useful during the layout process when various parts needed in a project are measured to ensure that they are tailored to the project's specifications. A Vernier height gauge can also easily be fitted with a scribing attachment so that lines can be scribed onto the parts under inspection. Their versatility makes them a widely usable tool in most workshops.
Vernier height gauges are also usable in metalwork and other types of crafting. Woodwork, with its emphasis on on-material notation and practical applications is perhaps their most direct application. They see use both in a commercial capacity and in the practices of hobbyists of many types.