Question: How do I create register-style bit width tick marks on merged cells, like wavedrom?

[bai-yi-bai]

Hello,

I am attempting to use prawn-table, via a custom AsciiDoctor-PDF extension, to create tick marks on merged cells, for use in displaying CPU registers. These tick marks are used to better indicate to the reader the width of the register. A comparable example is how wavedrom does this:

Link to this example

More examples

I'm attempting to create a similar representation without resorting to SVG, or wavedrom via kroki/other tool, by using prawn-table. The only thing I'm missing is the ability to add the bit width tick marks. One option, I suppose, is to simply move the cursor on the page and draw vertical lines, but I wondered if there was a more elegant solution.