I may be off here, and in a previous post on this.. but it's possible he could be wanting a contract surety bond which basically holds you responsible.. I would take great caution with this and seek advice from your attorney (preferably the one who helped with your contract)
Here is what I found:
Three types of surety bonds:
* The
bid bond assures that the bid is submitted in good faith and that the contractor will enter into the contract at the price bid and provide the required performance and payment bonds.
* The
performance bond protects the owner from financial loss should the contractor fail to perform the contract in accordance with its terms and conditions.
* The
payment bond assures that the contractor will pay specified subcontractors, laborers, and materials suppliers associated with the project.
Here's a link that is pretty straightforward:
http://www.sio.org/html/Obtain.html