Each bid must be enclosed in a sealed envelope which shall be clearly labeled with the words "Bid. This article provides a look at the construction bidding process for subcontractors, from bid release to the beginning of work.In this article, learn how to customize a construction proposal template that you can use when participating in bids. A bid proposal is a document used to outline a business's products or services when applying for a contract. Our construction bidding guide will take some of the mystery out of the process. Construction Bidding Process. In this blog, we will teach you how to write an effective construction proposal that stands out from the competition.