Finding 1/4" on a Sewing Machine

I have an old, mechanical Singer sewing machine that doesn't have a 1/4" foot on it, and it has lines marked on it, but no numbers printed on it to indicate what the lines are! This is the method I use to find 1/4" on it:
1. Use an acrylic ruler to mark 1/4" on a small piece of scrap paper (use a very fine point ink pen or a very sharp pencil to make the mark)
2. Drop the needle of the machine directly on the line you just drew:

3. Put a piece of masking tape directly beside the piece of paper. You can build a "fence" by using multiple layers of tape, if you want:

4. Raise the needle and flip the piece of paper to the other side. Sew down the length of the paper using the masking tape as a guide:

5. Remove the paper, flip it over, and make sure your stitches are directly on top of the line you previously drew. If it is, your masking tape is in the right position; if it's not, repeat this whole procedure until you get it exactly lined up.

Unfortunately, until I figure out a way to permanently mark the line, I have repeat this procedure every time I change the bobbin (because I have to remove the tape to get to the bobbin compartment).