{ 
  With this code you can create none border style (BorderStyle = bsNone) 
  but sizeable windows (forms) 
  First you must set BorderStyle := bsNone of your Form in Object Browser. 
  There is your small but forced code; 
} 

type 
  TForm1 = class(TForm) 
  private 
    { Private declarations } 
  public 
    { Public declarations } 
    procedure CreateParams(var Params: TCreateParams); override; 
  end; 

var 
  Form1: TForm1; 

implementation 

{$R *.dfm} 

procedure TForm1.CreateParams(var Params: TCreateParams); 
begin 
  inherited CreateParams(Params); 
  Params.Style := (Params.Style or WS_THICKFRAME); 
end;