Contour will unintentionally cut both sides

[ninthabandit]

 I want to cut just the blue area, not the yellow circled area

 

My method was to make a sketch line, and selected this line as a contour. Why am I cutting both sides? Thanks in advance!!

[a.laasW8M6T · Accepted solution]

Hi

you have multiple open chains selected and you can see by the red arrows on some of them that they are cutting on the wrong side of the line

see attached

[ninthabandit]

EDIT: I see how you did it. Thank you!