Steel windows are made from two flat pieces of steel that are then joined to create a bigger window. Each panel can hold glass and has an HT profile welded on the inside. The profile (or grouse) does the work of holding the glass in place while allowing for airflow.
The joints are filled with polysulphide sealant, which is a very strong glue-like material that helps to keep the window in place and keep out water and heat.