In Sweden, the normal design of a clay-tile covered roof is as follows: a wooden panel (19 mm thick plywood or tongue-in-groove boards) is nailed onto the rafters and covered with roof felt; counter-battens (ströläkt) ar laid on the panel in the direction of the roof slope with max 600 mm spacing; and finally the battens proper (bärläkt) are nailed to the counter-battens with a spacing to suit the used roof tile.
In Britain and on the Continent, roofs are often built without a wooden panel and without "ströläkt"; the battens are fastened directly to the rafters.