Sort of what Furry says, though not the drop outs. Lynn of CustomMotoredBicycles.com demonstrated on one of my visits. With a bike frame on it's side in her driveway, she put her foot on the lower junction of the seat and chain stays.
Grabbing the opposite side she hauled away and sprung the frame sections. I consider Lynn a petit lady, but I surely underestimated her power. I tried springing my Worksman frame and got nowhere, darn 4140 tubing is tough!
Tom from Rubicon