Yes, mitsakes (Mistakes) happen. Back when you were using a manual typewriter, there was no backspace or spelling / grammar squiggles under your word to tell you you got it wrong. What were your options?
Strike out ( x’s).
Yup, that was a thing. Just x it out and keep going. It gave you some character. Of course, if you found it after you were past it on a different line, lining the page up to x it out was a pain.
Did you know that Michael Nesmith (of the Monkees)’ mom invented Liquid Paper? Bette Nesmith created a water-based tempera paint tinted to match the typing paper. She put the liquid into a clean nail polish bottle in order to take it to work with her.
Simply place them over the letter you want to erase, remove them from between the typebar guides, and retype the correct letters.
Editor Bonus: Check out the 2014 article from the Getty, about Medieval Copyediting including topics as Medieval WhiteOut, and Strikethroughs; includes phenomenal medieval imagery.