A low cost, lightweight frangible wing slot seal can be applied to a guidance wing slot of a folding fin aerial rocket or missile, providing a barrier against exposure of internal missile components to external contaminants, while allowing unhindered deployment of missile guidance wings simply by bursting through the seals. The simple design is nearly foolproof, and has no impact the likelihood of weapon failure. The seal is a flexible sheet which is sufficiently thin so as not to exceed the required volume envelope of the missile. The sheet includes a burst seam, which is breached when impacted by the leading edge of a deploying wing. No additional wing deployment force is required, and after deployment the seal has minimal impact on the aerodynamic performance of the wing.