The term 'letter-shaped hardware' refers to two types of fasteners: a tnut and a ubolt. A tnut is a type of nut that has four prongs that form a 'T' shape, allowing it to be inserted into a slot in a piece of material. A ubolt is a type of bolt that has a U-shaped bend in the middle, allowing it to be used to secure two pieces of material together. Both tnuts and ubolts are commonly used in construction and engineering projects.