import cadquery as cq
w0=cq.Workplane('XY',origin=(0,0,18))
r=w0.sketch().segment((-50,-23),(50,-23)).segment((50,20)).segment((21,20)).segment((21,9)).segment((-19,9)).segment((-19,23)).segment((-50,23)).close().assemble().finalize().extrude(-37)