Many construction companies struggling through a difficult economy are facing yet another obstacle, the tightening market for surety bonds, according to contractors and insurance brokers working on their behalf. These bonds protect public construction projects and many private ones in case a contractor fails to finish a job. What generally happens then is a third-party insurer pays to finish the work of the defaulting contractor. But due to a sustained real estate slump, with many contractors' credit scores plummeting, especially among smaller companies, obtaining these required bonds has become increasingly difficult. Most underwriters, concerned about companies folding during jobs, are making it tougher for those most at-risk. Still, many institutions have implemented a SBA surety bond guarantee program for those that may qualify.