the jigs

[Ricky]

hi im trying to get some info on the jig in fig 5.15 in the picture it shows you the length of the plate is 465mm but in the wrighting below it says the length is 475mm now it gives you 10mm extra is that 10mm for you to weld the box section on or is that a mistake or what and in fig 5.18 it does the same thing length of the plate 315mm in the picture and the wrighting below it says 325mm and again it gives you 10mm extra so what is that 10mm for