Possible Clues:

• Often the line to sign on
• Sign on the - line
• Having a pattern of small round marks
• . . . . . . the Is and crossed the Ts
• Sign on this line to authorise
• Sounds as if I should be 20 downed
• Like some notes on a music sheet
• How I was finished with writing? Not in that case
• ... the `i's and crossed the `t's
• . . . . . . the i-s and crossed the t-s