a = 30; // length of piece
b = 1; // thin side of bottom taper
w = 12; // width of piece
c = 5;
d = 1.5; // thick side of bottom taper
e = 10;
f = 12;
g = 4;
h = 7; // offset of hole place from edge
hole_radius = 0.9;

module piece(){
   translate([0, w, 0])
rotate(90, [1, 0, 0])
linear_extrude(w) {
    polygon([[0, 0], [a, 0], [a, b], [c, d], [c, e], [g, f]]);
}
};

difference(){
    piece();
    translate([a/2, w/3, -1])
    cylinder(5, hole_radius, hole_radius, $fn=60);
    translate([a-h, 2*w/3, -1])
    cylinder(5, hole_radius, hole_radius, $fn=60);
}