I'm not sure how to describe this without a picture:
Is there a way to do this without drawing the lines manually? Preferably the lines will look as shown.
You can create a table that includes the label and all the letter slots, then set widths and borders.
For example, suppose you want 9 letter slots:
And there you have it:
This is what it looks like in Print Preview:
The advantage of this method is that the user can move from cell to cell using the Tab key, and also cannot accidentally break the structure.
You can do this with unicode chars.
This is a left box, a middle bit and a right box corner, with a bottom bit to widen it. You get this holding Alt and hitting the keys on the number pad. Note that this must be done in an Office app or one that supports Unicode codepoints (otherwise the 4 digit code will be modulo 256 and so wrapped to a number less than 256).
┗ : 9495
┻ : 9531
┛ : 9499
━ : 9473
Or you can just cut and paste from here.