I use them mostly for scratch building, holding things square, fixturing and use them to sit the frame on as I am building the truck. No they are not necessary, they are just a nice additional tool. A more important tool is my calipers, for instance I build a 4 bag air suspension and the molding process had some air bags at different heights, which when done you could possibly have a set of wheels that will not touch the table as the other wheels do ( one set hanging in the air).