Scottish joke

An old Scotsman is sitting with a younger Scottish gentleman and says to the boy, "Ah, lad, look out that window. You see that stone wall there? I built it with me own bare hands, placed every stone meself. But do they call me MacGregor the wall builder? No!"

He takes a few sips of his beer then says, "Aye, and look out on that lake and eye that beautiful pier. I built it meself, laid every board and hammered each nail, but do they call me MacGregor the pier builder? No!"

He continues: "And lad, you see that road? That too I build with me own bare hands. Laid every inch of pavement meself, but do they call MacGregor the road builder? No!"

Again he returns to his beer for a few sips, and then says, "Agh, but you screw one sheep. . . ."