Next up is to flatten the base on a machine using a mix of different grit belts and a stone grinder. A flat base is important as it means the angle of your edges are true. It’s down to the knowledge of the ski technician as the process involves a certain level of skill and an eye for detail. A good technician will know how much to grind off depending on the brand of ski or how old it is.
The most important part of a tune is the structure of the base, this is the pattern that you can see when you turn the ski over. Without a structure, the ski/board will run slow and not as responsive as it should.
A structure is a very light pattern that is etched into the ski/board by using a stone grinding machine. In essence, the structure allows water to channel out of the base allowing for a smoother glide in snow by working with the wax that has been applied. Ski workshops will create their own structure to suit the conditions of local mountains, but here is a rough explanation of how it works.