A process for simulating and assembling flexible parts includes creating an ideal path between first and second planes and placing a virtual rigid envelope around the ideal path, and possibly tubular extensions beyond the path. A virtual flexible part is marked with reference features and pulled through the virtual rigid envelope, such that the path of the virtual flexible part is constrained but may rotate. Removing the virtual rigid envelope allows the virtual flexible part to relax, causing it to move to its lowest energy state. Zero-twist end conditions on the virtual flexible part are marked, corresponding to the intersection of the reference features with the planes. Identification marks are placed on a real flexible part, corresponding to the reference strips on the virtual flexible part. The real flexible part may then be assembled by aligning zero-twist marks on mating features to the identification marks on the real flexible part.