Create a new word document file, and click Insert-Table to insert a table with only one row and one column.

Left-click the "+"in the upper left corner of the table and select "Table Properties" to modify the length and width of the table.

In this example, by default, the width is the same as the width of the document. We just need to modify the length. Click the line, select the specified height, enter 24 cm in this case, and then click OK.

A separate border is generated.

Click the "+"in the upper left corner of the table, select the color fill button, and select dark gray, and a single table will be filled with gray.

Put the cursor in the table, enter any text (please choose a white font color, otherwise you won't see the cursor and text), press enter, and insert a single table of 1× 1 as in step 1. The purpose of entering text and pressing Enter is to form an edge between the newly inserted table and the original table.

Delete the text and change the color of the internal table to white, as shown in step 5; Change the row in the inner table to "19 cm". Click the Center button to center the two tables; So a gray border is finished.