About the Thicken Tool in Sketcher
You can use the Thicken tool to add material thickness in Sketcher mode during the creation or redefinition of the following types of wall:
Extrude
Revolve
Flange
Helical sweep
Click Setup > Feature Tools > Thicken. A thicken line, offset from your sketched line, represents the opposite side of the wall.
1. Thicken line
2. Sketch line