Blaylock Partners LP, an investment banking and securities brokerage firm, relocates its headquarters to occupy 23,000 square feet, the entire 15th floor at 399 Park Ave, the space the firm took over from Lehman Brothers. Alex Chudnoff, Steven Bauer, Paul Glickman and Paul Amrich of Cushman & Wakefield represented Blaylock while Insignia/ESG's Robert Alexander, Michael Geoghegan and Eric Engelhardt acted for Lehman. Blaylock's new home comes out of the city's much-discussed "shadow space" inventory - space that tenants like Lehman quietly hope to unload without actually announcing its availability. "It wasn't actively on the market," Chudnoff said. "It was a well-hidden, below-market opportunity." The firm is leaving behind 15,000 square feet at 609 Fifth Ave. and will stay at the new office for about 14 years.