A device for forming structurally stable curved structures includes an elongated element (10) with a number of segments (12) interconnected at effective hinges (14) to allow deflection of each segment relative to adjacent segments between a reduced-curvature state and a flexed state. Neighboring segments have interlocking features (16) forming an inter-segment locking configuration such that, when the segments are deflected from the reduced-curvature state to the flexed state, the interlocking features interlock adjacent of the segments so as to retain the segments in the flexed state corresponding to a predefined curved configuration of the elongated element. Additionally, or alternatively, a leading portion (44) and a rear portion (40) of the elongated element have features forming at least part of a loop-lock configuration effective to lock together the leading portion and the rear portion so as to form a closed loop structure.