Hardwood, engineered hardwood, laminate, and vinyl plank all require an expansion gap around the perimeter. I can understand this on a floating floor, but they require it even with nail down, or glue down. What I don't get is this: if the board is glued down, then to expand at the end of a row even a little, the glue joint would have to fail. I don't see how a glue joint could stretch a quarter of an inch and not fail. The same with nailing - for the end of the row to expand a quarter of an inch, the nail would have to break off. So I don't see how it makes sense to leave much of a gap if gluing or nailing. What am I missing???