bays = 5;
wt = 2;   // wall thickness
pt = 12;  // phone thickness
l = 170;  // length
h = 40;   // height
w = bays * (pt + wt) + wt;
lip = 10;

T=atan((h - lip + 0.5) / l);

difference() {
  union() {
    cube([w, l, wt]);   // base
    cube([w, wt, lip]); // front lip

    // back
    translate([0, l - wt, 0])
      cube([w, wt, h]);

    // side walls
    for (i = [0 : bays]) {
      translate([i*(pt + wt), 0, lip]) rotate([T, 0, 0])
        translate([0, 0, -h]) cube([wt, l / cos(T), h]);
    }
  }

  translate([-wt, -wt, -h]) cube([w+2*wt, l+2*wt, h]);  // bottom
  translate([-wt, -wt, h]) cube([w+2*wt, l+2*wt, h]);   // top
  translate([-wt, l, -wt]) cube([w+2*wt, l, h + 2*wt]); // back
}
/*
sin(ang) = opp / hyp
ang = asin(opp/hyp)
cos(ang) = adj / hyp
hyp = adj / cos(ang)
*/