T-shaped steel tees are commonly used in construction and engineering applications where a strong and stable connection is required between two perpendicular beams or columns. They are designed to provide support and stability to the structure, and are often used in the construction of bridges, buildings, and other large structures.

Y-shaped steel tees, on the other hand, are typically used in applications where a connection is needed between three beams or columns that meet at a common point. They are often used in the construction of trusses, towers, and other structures that require a strong and stable connection at multiple points.

When choosing between T-shaped and Y-shaped steel tees, it is important to consider the specific requirements of your project, including the load-bearing capacity, the size and shape of the beams or columns, and the overall design of the structure. You should also consider the cost and availability of each type of tee, as well as any other factors that may be relevant to your particular situation.