If you’re looking to tune your table saw, referencing from a blade isn’t the most precise way — the blade could be warped or dirty, and those sharp teeth can get in the way. To combat this problem and give you the most precise alignment possible MasterGage sells their MasterPlate, a solid 6″ by 10″ by 3/8″ aluminum plate that replaces the blade while you tune your saw.
MasterGage machines the MasterPlate to within thousandths of an inch. Depending on which way you mount the MasterPlate it gives you 10″ of parallel surface or 7″ of vertical surface with which to square the table and the fence. Not only does it work on table saws with 5/8″ and 1″ arbors, it can also help align your radial arm saw or miter saw.
If you’re looking for the most accurate setup you can get, you could do worse than spend the $50 for the MasterPlate.