[NTG-context] MetaPost cutdraw

Hi, I’m trying to understand MetaPost better. I’d like to draw a fat line that’s cut at its end points. I learned, “cutdraw” should do the trick, but I get a parallelogram instead of a rectangle. What’s wrong? Hraban \startMPpage draw (0,20)--(20,20) withpen pensquare scaled 10; cutdraw (0,0)--(20,0) withpen pensquare scaled 10; % just to show start and end draw (0,-10)--(0,30); draw (20,-10)--(20,30); \stopMPpage