Building not fully enclosed. In any district, other than as residence district, any use which is nonconforming because it is not located within a building fully enclosed on all sides may be continued for three years after the effective date of this chapter, provided that, after the expiration of that period, such nonconforming use shall be terminated. Any other provision to the contrary notwithstanding, however, no such use will be required to terminate if, within said period, such use shall be located within a completely enclosed building complying with the requirements of the district in which it is located or if, within said period, such use shall be surrounded with a solid fence, of material and design acceptable to the Planning Board, which fence shall be one foot higher than any material stored outdoors, provided that such fence shall be maintained in good condition at all times.