We do not fill up the entire page with the sketch, we leave an appropriate amount of white space for visual purposes, as well as for the frame and mat. Some dresses are fuller or have accessories (small back, bouquet, shoes, etc), which will overflow from the parameters we draw in.
Some dresses are not full, which will have the dress not overflow from the parameters. Our parameters we draw in are not always centered on the page if we have accessories. *the rectangle lines and numbers will not be on the final sketch.
Negative space is, quite simply, the space that surrounds an object in a image. Just as important as that object itself, negative space helps to define the boundaries of positive space and brings balance to a composition.(source: Creative Blog).