A retractable tape spring in-building method for a deployable structure comprising a main tape spring having an axis of deployment and of refurling substantially parallel to an unfurled axis X and comprising two ends, a secondary tape spring comprising two ends and a winding mandrel carried by a shaft parallel to an axis Z perpendicular to the axis X, the main tape spring being wound around the mandrel, a first end of the main tape spring being fixed to the mandrel, the method comprising the following steps: fixing a first end of the secondary tape spring a predefined distance away from a second end of the main tape spring, fixing a second end of the secondary tape spring on the mandrel. A deployable structure comprising a tape spring for a flexible structure is also provided.