Hi. The sketch below will be used with a revolve to create a hollow tube with 3.5mm internal diameter. To get a 3.5mm internal diameter I need to create a dimension of 1.75mm as shown. I remember once reading a trick which would allow me to show the dimension as 3mm, I think it involved holding some key when creating the dimension. I think it then shows the dimension as being across the x-axis. Does anyone know what I mean? And recall how it's done?