I have that 3D sketch that I want to convert into a body.
You can loft a profile to a point using guide curves.
You can create planar surfaces, knit them into a solid body and then combine with the main body.
You can use 3D sketch to create a feature but can't covert it into a body
The other way is to use covert entities
Jimmy, if you attach the file, we can have a look at how it might be best done in this case.
But I think that a loft or a boundary maybe what you're looking for.
Select the back Surface and insert a sketch
Convert these lines to sketch lines and extrude up to the X
Select the line and point and add a plane
Make a sketch there and use the extrude cut through all
Make a three sided Surface and kint to make a solid..
Did you tried to use delete face too?
2017 SOLIDWORKS Help - Delete Face
Option "Deleting and patching"
2017 SOLIDWORKS Help - Deleting and Patching Faces
Retrieving data ...