A tuple is a fixed fixed-length list containing elements that need not have the same type. It can be, and often is, used as a key-value pair. A row (sometimes called a record) is the set of fields within a table that are relevant to a specific entity.
The stem wall on a concrete foundation is essentially the supporting wall that joins the foundation of a building to the vertical walls of the structure that is constructed atop the foundation.
What type of wall are the shelves being fitted on, is it brick or is it a studded wall, what is going to be stored on the shelves, take into account the size and weight of the items and also the clearance needed between additional shelves.