i want to append the tr row in the table..the code doesnot works well!

i want to append the tr row in the table..the code doesnot works well!

  <script>
            $(document).ready(function() {
                $("#tbl_add").click(function(){
                     $("table").append("#thi");
                });
              });
        </script>

    </head>
    <body>
        <div id="Case">
       <div id="CaseTable">      
<form>
    <table border="1">
        <tr>
            <td>Label</td>
            <td>Find By</td> 
            <td>Event</td>
            <td>Data</td>
          
        </tr>
       
        <tr id="thi">
           
            <td><input type="text" id="TestName1" name="TestName1"></td>
            <td><input type="text" id="TestName2" name="TestName2"></td> 
            <td><input type="text" id="TestName3" name="TestName3"></td>
            <td><input type="text" id="TestName4" name="TestName4"></td>
        </tr>
       
    
       
      </table>
   </form>
   </div>
        <div id="add">
            <button id="tbl_add" >ADD</button>
        </div>