scale(10){
difference()
{
    square([48,34],true);
    
    translate([21.5,7.5])
    {
       square([3,4],true); 
    }
    
    translate([21.5,-7.5])
    {
       square([3,4],true); 
    }
    
    translate([-21.5,7.5])
    {
       square([3,4],true); 
    }
    translate([-21.5,-7.5])
    {
       square([3,4],true); 
    }
    
    
    
}}