What does BLKTS stand for?

Blankets

Fiber-glass or rock-wool insulation that comes in long rolls 15 or 23 inches wide. OR To install a box or barrier within a foundation wall to prevent the concrete from entering an area. For example, foundation walls are sometimes "blocked" in order for mechanical pipes to pass through the wall, to install a crawl space door, and to depress the concrete at a garage door location.