The "handwriting", cheirographon, was a term used for a promisory note, a note of indebtedness. Paul wrote to Philemon that if Onisemos owed anything, that Paul would pay it back,
Philemon 1:19 KJV
I Paul have written it with mine own hand, I will repay it: albeit I do not say to thee how thou owest unto me even thine own self besides.
To get credit, you'd write in your own handwriting your promise to pay. When you paid, the one you owed would write "finished" on it, and that would be your receipt. Archeologists learned this from the so many parchments found in the ancient landfill outside Oxyrhynchus in Egypt.
The "cheirographon", that is, my personal handwritten certificate of indebtedness to the Law was blotted clean.
Colossians 2:14 KJV
Blotting out the handwriting of ordinances that was against us, which was contrary to us, and took it out of the way, nailing it to his cross;
Much love!