Usually when doing sign design the border is created at the end and it size depends upon the contents. However sometimes we have a particular sized sign we want to create. It is a bit like doing sign design in reverse, where you know the size of a sign border and just want to add certain text within that sign border.
This can be done by using the XBLOCK command, which can be found on the rectangular border menu items.
A dialog will open asking for the x height and sign sizes you require, and from this information the sign border will be created.
Both a flag sign or a rectangle stack sign border can be created using this command.
The sign is still drawn in stroke width units, so it is important to put the correct x height into the dialog in order for the border to be created to the proper size. It might be worth creating two or three borders with different x heights, so you can then see from which of the x heights the text will fit best into the sign border. It is important not to scale the text up or down in size, the standard 8sw high text is still used with this type of sign.
If you find it odd that a smaller x height produces a bigger sign face, this is actually correct because you can fit more 'small text' inside the sign border than 'bigger text'.