D4 stands for "Deuce 4", John Middendorf's Yosemite Valley nickname (in the heyday of the Yosemite Rescue Team, in the 80's, everyone got a nickname whether you liked it or not). Deuce derives from my friends first calling me "Dusseldorf", then Deuce, and the 4 comes from the fact that I was born John William Middendorf IV, and once that became known, the number 4 has followed my nickname ever since.
In the 1980's and 1990's, we revolutionised the sport of extreme remote big wall climbing, with the advent of the first truly stormproof portaledges from A5 Adventures, Inc, which offered engineered hanging platforms that allow multiple day climbs to be accomplished safely and with adequate rest in any weather. By 1997, the state of the art A5 Portaledge could withstand any conditions, and the A5 design was duplicated by all the other manufacturers. For the 20 years, not much changed in the art of portaledge design, until the advent of the D4.
The successful 2017 D4 Portaledge Kickstarter has spawned more innovation in hanging platforms and collapsible structures. Enjoy!