Point supported glass curtain walls use stainless steel castings called glass spiders. These are the parts used to connect the glass sheets. The spider is then held in place by a support system which can consist of different elements such a steel cables and steel / aluminum columns ect.
This system allows for movement and adjustment in the glass curtain wall. Being a system that is exposed to the elements and also stress means that the material properties and quality control is critical in producing these castings.
The other required parts to complete the system is the glazing and silicon. These products also need to meet certain standards to function correctly.