difference(){

  	linear_extrude(height=4)
  		import (file="ecrou.dxf", layer="0", $fn=100);
	
	union(){
		translate([0,0,2])
			linear_extrude(height=2.4)
  				import (file="ecrou.dxf", layer="nut-fingerprint", $fn=100);
		translate([0,0,-0.1])
			cylinder(r=1.6,h=5,$fn=50);
	}	

}