swifts nest in colonies, tend to keep the same nest for life, and require nests to be fairly high up & sheltered.

hollow bricks like this allow swifts to do what comes naturally to them, with v minimal change on our side of things, since they're just being added during the building process & not being retrofitted.

individual bird boxes in trees etc can be great for other birds, but it'd be tough to convince swifts to use them!