This excerpt taken from the PNC 10-Q filed Nov 8, 2007.
Standby Bond Purchase Agreements and Other Liquidity Facilities
We enter into standby bond purchase agreements to support municipal bond obligations. At September 30, 2007, the aggregate of PNCs commitments under these facilities was $238 million. PNC also enters into certain other liquidity facilities to support individual pools of receivables acquired by commercial paper conduits including Market Street. At September 30, 2007, our total commitments under these facilities were $8.0 billion, of which $7.8 billion was related to Market Street.