On Thursday contractors plan to top out a seven-story, 28-unit apartment building known as the Stack on an infill site in Upper Manhattan. The event would be unremarkable, except that four weeks ago, the only part of the structure that had been erected on the 50-foot-wide by 150-foot-long lot was the first floor framing. Now it is completely enclosed, and has its interior partitions as well as plumbing fixtures, countertops, doors, and hardware—even the toilet paper dispensers have been installed. The Stack, designed by architecture firm Gluck+ (formerly Peter Gluck and Partners), has gone up so quickly because it is composed of 56 steel-and-concrete modules built in a factory in Berwick, Pennsylvania. These components, which make up the studio, one-, two-, and three- bedroom apartments, have been trucked to the site with all interior finishes in place and stacked by crane at the rate of about four per day since June 19.