D4 (Deuce 4) has been my nickname ever since engineering school and my early years in Yosemite.
My first big foray into climbing gear design was a big wall hammer, and a new nut based on a sphere and grooved wedge, which later manifested in the "ball-nuts" and "monkey paws". I then went on to form A5 Adventures, which became a global melting pot of new ideas and products in the realm of lightweight specialised equipment for remote expeditions.
Then I studied a bit more engineering and architecture, and had a series of professions in design.
My main current design work is Big Wall Gear D4 Portaledge, linked here: http://bigwallgear.com
A5 revolutionised the tools for Big Wall climbing in the 80's and 90's
A5 Portaledge Development. A5 Portaledges enabled a huge boom in big wall standards in the 1990's because for the first time, climbers were able to withstand Himalayan type storms. The innovation continues with the new D4 Portaledge Design at http://bigwallgear.com
A5 Haulbags --all current haulbags "borrow" ideas from the original A5 design, including the "tuckaway" shoulder straps (an A5 first), the waterproof closure, the offset clip-in, and many other features now standard on many modern packs and haulbags.
John Middendorf's ulta-lightweight single portaledge featured in the Flexibility exhibition in Turin.
A5 designed a range of new equipment, a lot of our designs have since been copied and become standard tools. A5 design was an alternating process of field testing and building prototypes in the shop.
Above are Middendorf's notes written on a back page of a book he was reading during an ascent of El Capitan with new ideas. But A5 was a team effort--here, the 1995 team and the original A5 "credos" on the shop wall.