Tomas wanted a boat that cost 12 coins, but his book was blank, since this was a first loan. Mr. Fenn said he would lend if someone with a tidy book helped.
To co-sign is to sign the same loan: two names on one paper. The second name promises that if the first cannot pay, the second will.
That is a big promise, so a helper asks, could I pay all of it? The loan sits on both pages, and every payment, on time or late, shows on both.
When a storm stopped Tomas paying in month three, the bank turned to Rosa, and she paid. Tomas paid her back in month four. A kind no is okay too.