I'm a student trying to model a framing bracket like the one here (http://www.pryda.com.au/wp-content/uploads/2016/08/FB-RANGE-Framing-Bracket.jpg). I made a 3D sketch of the surface, now all I need to do is to make it 1 mm thick.
But when I try to do "Filled Surface" on it it tells me "The boundary is open and cannot be patched". If I try it again with "Fix up boundary" selected, it tells me "Failed to close boundary. The boundary cannot be patched".