restart;
C:=plots:-cylinderplot(0.5,theta=0..2*Pi,z=0.5..0.5+1/sqrt(2),
                       style=surface):
rotC:=plottools:-rotate(C,-3*Pi/4,[[0,0.5,0.5],[0,-0.5,0.5]]):

plots:-display(
  rotC,
  plot3d([x-1/2,x+1/2],x=-0.5..1,y=-0.75..0.75,
         style=surface,color=gray,transparency=0.5),
  scaling=constrained, view=-0.5..1
);