Method One:
① Select the form and click on the Design menu bar.
② Click the drop-down arrow to the right of the pen style and select a double line in the Drop-down menu, as shown in the picture.
③ Click the drop-down arrow on the right side of the "Border" and select the area you want to make a double line in the Drop-down menu, with an example of "outer-side frame".
④ the wireframe on the outer side of the table has become a two-line table.
Method Two:
① Select the table, click the right mouse button, and select Table Properties.
② Select the Borders and Shading button in the Pop-up Table Properties page box.
③ in the "Borders and Shading" page box, select the double line in the style bar, the border bar can be selected according to your own needs, here with "all" examples, and then click "OK" button.
④ at this point all the wireframe has become a double line, the two-line form has been completed, as shown in the figure.