How to extrude from multiple faces on a body. Or to avoid this problem, how do you combine faces of a body so it is one uniform workpiece?

[jeppe489BC]

Like title says, I am trying to extrude this sketch from the curved body, but I get the error that it is outside the face boundary. How can I fix this? appreciated very much. Thank you in advance! Pic attached of body and sketch

[davebYYPCU]

No file, we guess, 

extrude into the body, and depending on your intent, you can cut and trim sections.

Might help....

[jeff_strater]

hard to say without more information, but if you are doing a "To Object" Extrude, you may just need to select "To Adjacent Faces".  This setting allows the Extrude to terminate to faces which are adjacent to the one selected

[mango.freund]

do "split body" and "keep tool" cutting line is your sketch. greetings mango