Hotel room blocks?

Are you asking what a hotel block is? Some couples ask a hotel or hotels to set aside a group of rooms so that guests can book, sometimes at a discounted rate from what they can get themselves, but not always in my experience. The advantage is that the rooms are set aside, so that all or a number of guests can stay at the same location, making it more convenient for things like transportation to a venue, rehearsal dinner or day after brunch. Sometimes rooms need to be reserved by a certain date, even before invitations go out in order to ensure availability. Info about room blocks can be shared on a wedding website and or an insert in the invitation or save the date.

If you have guests coming from out of town who will need to stay in a hotel, couples often setup room blocks at a hotel or two. This guarantees that their guests will be able to find a room, especially if the wedding will be held in a popular area or if there's a large event (concert, convention, festival, etc) in the area that same weekend that would cause a high demand for hotel rooms. There are a few different ways that room blocks can be set up, but the most common one is a courtesy block: the hotel reserves a set number of rooms (usually 10 or 20), and sets a deadline (usually around 4 weeks before the wedding) and a price. Often, there's a small discount for booking in a room block. Guests have until the deadline to call and reserve one of the rooms in the block, and the responsibility for the cost of that room is on the guest. If all rooms in the block are booked before the deadline, the hotel will add another set of rooms to the block, depending on if any are still available. Any rooms that are not booked by the deadline are released back to the hotel for them to sell to someone else. There is usually no cost or obligation to you for setting up a courtesy room block.