$fn=100;
minkowski(){
cube ([5,16,0.5], center=true);
cylinder(r=1.5,h=1);
rotate([0,90,0]) cylinder(r=0.4,h=1); 
}  
minkowski(){
translate ([-0.5,0,-2]) cube ([0.01,8,5], center=true);
//cylinder(r=0.5,h=1);
translate ([0,0,3]) rotate([0,90,0]) cylinder(r=0.4,h=1); 
translate ([0,0,3]) rotate([0,90,90]) cylinder(r=0.4,h=1); 
}