I say, and with God's help: It has become customary to sell goods in warehouses, whether the sale is from exhibitions or stock exchanges. The possession does not occur merely by receiving a document that proves the right to the sold item, even if it contains a specific number identifying the sold item, unless the buyer agrees to the retention of the sold item either verbally or by custom. In that case, he would be considered as possessing it by law, and the retention of the sold item in the warehouse would be considered a deposit. Similarly, if the sold item does not have a specific number but has been identified in some way and left in the warehouse, he would be considered as possessing it, and its retention in the warehouse would be in the capacity of a deposit. Our Sheikh has presented methods for possession in warehouses in the jurisprudence of sales (2: 393 - 402), but what I have mentioned is sufficient, and God knows best.