The following code demonstrates how to implement illusion of the flat control for acCheckBox component (how to make checkbox with flat borders be 3-dimensional when the mouse hovers the control).
// OnMouseEnter procedure TForm1.acCheckBox1MouseEnter(Sender: TObject);
begin
acCheckBox1.Ctl3D := True;
end;
// OnMouseLeave procedure TForm1.acCheckBox1MouseLeave(Sender: TObject);
begin
acCheckBox1.Ctl3D := False;
end;