The main difference between the Arrival restriction and the Through restriction is in how they automatically adjust or relax based on existing reservations for that room. The Arrival restriction will automatically relax if it is blocked on the right by a reservation in the future. The Through restriction will automatically relax only if blocked on both the left and right. The most common restriction is the Through restriction. The use of the Arrival restriction is typically used only on the first night that a restriction would apply. Only set one type of restriction per block. If both are used, the Through restriction trumps it.
Minimum Nights on Arrival:
If a guest is arriving on a date that has Minimum Nights on Arrival set, they must meet the minimum nights indicated, if possible.
If reservations have previously been made that make the minimum nights set impossible for that room, then the minimum nights will automatically be adjusted/relaxed. For example, if Friday has Minimum Nights on Arrival set to 2, then someone who tries to book a room for a Friday check-in must stay at least two nights: Friday and Saturday night. If Saturday is already reserved for that room, it would be impossible for the guest to stay the required two nights. In this case, the Minimum Night on Arrival for Friday will automatically adjust to 1, allowing you to fill the room.
Below is an example of Minimum Nights on Arrival programmed for three nights from the 30th to the 4th, and two nights on the 7th and 8th.
The gray boxes indicate reservations, so you're aware of your supply.
Below you'll see what the above programming looks like when the automatic adjustments are applied based on the reservations that exist in the system. You can see a guest checking in the 3rd is allowed to stay one night in 3 rooms. This is because the 4th is reserved for three rooms, making it impossible to arrive on the 3rd, and stay more than one night.
Minimum Nights Through:
If a guest is staying on a date that has Minimum Nights Through set, they must meet the minimum nights indicated. If reservations have been made that make the minimum nights impossible, then the minimum nights will automatically be adjusted. For example, if Friday has Minimum Nights Through set to 3, someone who tries to stay Thursday and Friday must stay at least one more night. If Wednesday and Saturday are already reserved, then the Minimum Night Through for Friday will automatically adjust to 2.
Below is an example of Minimum Nights Through programmed for three nights from the 30th to the 4th. The 7th and 8th are programmed for a two night minimum.
The gray boxes indicate reserved rooms, allowing you to see your supply.
Below you'll see how the minimums automatically adjust based on the reservations made. Note the differences between the automatic adjustments made here compared to those made in the Min Nights on Arrival restriction above. The system will only relax the restriction if blocked by existing reservations on both sides, instead of just on the right.
Related: How to Set Your Minimum Nights