The following steps is about creating a rectangle with right angle symbols in each corner in C3PO using table.
Example:
1.1. Click the "Insert table" icon on the menu bar.
1.2. Highlight the number of cells needed.
2.1. Click the cell that you want to modify.
2.2. Click the "Table Properties" icon on the menu bar.
2.3. Click the "Table Alignment" drop down and select the desired alignment.
2.4. Enter the column width.
2.5. Click "SUBMIT" button.
3.1. Highlight the cell/s that you want to add the border to.
3.2. Click the "Border Style" icon and select the desired style.
NOTE: This will not be visible on eBook.