Dwight, who owes Jim $200, draws a check payable to Jim on his checking account at American Bank. Dwight signs the check but leaves the amount blank. Jim then fraudulently fills in $2,000 and presents the check to American Bank, which pays it. American Bank can charge Dwight's account $2,000. Dwight's only recourse is to sue Jim. Dwight's check is an example of what? Explain.