Abstract: This invention relates to a portable shelter or tent enclosure having a self supporting frame structure that may be pivotally erected and collapsed for supporting a fabric cover. The frame comprises at least three substantially U-shaped frame members which are linked at the ends of each of the parallel side arms remote the top of the U at about a common point. At least two of the three frame members are braceable in an angularly spaced apart position by segments comprising a pair of laterally braced parallelograms pivotally linked to the pairs of side arms. The frame structure has a removably securable horizontal frame brace that is easily connected to and removed from the top of the laterally braced parallelogram of the frame and includes arms extending angularly downwardly to the side from the brace to the parallel side arms forming the base of the laterally braced parallelogram thereby providing an effective lateral brace to the frame.