Lock has climbed with several leading high-altitude Himalayan mountaineers, including Anatoli Boukreev (K2 in 1993), Göran Kropp (Broad Peak in 1994), Doug Scott and Wojciech Kurtyka (Nanga Parbat Mazeno Ridge in 1995), and Iván Vallejo & Iñaki Ochoa de Olza (Annapurna 2007). After Ecuadorian Iván Vallejo, Lock is the second, and still the only other, Southern Hemisphere climber to complete all 14 eight-thousanders.