First of all, we need to look at your tender requirements, basically the tender have written seal format, not in accordance with the requirements of the tender seal, not open the bidding are directly to you into a waste of the bid! If you really do not have before you can follow what I said to you to ah!
Basically written in accordance with the format of the cover of the tender, and then add a sentence in so-and-so time before not to open! And finally add a seal at the seam of the seal! For example, below