||Make 50 golden fasteners. The two [groups of] tapestries will then be able to be joined together, so that the tabernacle will be one piece.
Ve'asita chamishim karsey zahav vechibarta et-hayeri'ot ishah el-achotah bakrasim vehayah haMishkan echad.
Keres in Hebrew. Some say that they were shaped like knees (Ibn Ezra from Isaiah 46:1); they were therefore angular in shape, something like a staple (Maaseh Choshev 4:2). Others say that they had hooks at both ends to go through the loops (Radak, Sherashim). Still others describe them as being 1/2 fingerbreadth long (3/8'), with bulbs at both ends to go through the loops (Rabbenu Meyuchas).
The entire array was therefore 28 x 40 cubits (42' x 60'). As we shall soon see, the interior of the tabernacle was 10 x 30 cubits. Since the beams were one cubit thick, the exterior dimensions were 12 x 31 cubits. The height of the tabernacle was 10 cubits (Exodus 26:16). Therefore, when the tapestries were placed over the beams, they left the lower 2 cubits of the beams exposed on the sides, and the lower cubit exposed in the back.
There is another opinion (see Exodus 26:24) that the beams were wedge-shaped, only one fingerbreadth (3/4') on top. According to this, the outer dimension of the beams on top was only 10 x 30 cubits, and only the lower cubit of the beams was exposed on the sides. This was the part of the beams covered with the bases. In the back of the tabernacle, even the bases were covered (Shabbath 98b).
According to another opinion, only the bottom cubit was exposed all around (Josephus 3:6:4).