A TSD donation setup. Given its name because of how the edge looks similar to stairs (階段, pronounced kaidan in japanese, means stair). While the overhang can vary, the T-Spin shape is always made with a S or Z.
The steps don't have to be at the edge:
Or you could build the wall part yourself:
Kaidan is a useful technique to use when you're trying to fix the parity of your stack.
Compare with some less-than-ideal alternatives:
Kaidan can be considered a subset of SZ prop, where a S or a Z piece is propped up in order to help create a T spin shape.
SZ prop can be combined with donations:
Compare with this donation technique:
Once you get familiar with this technique, you can place your S/Z first and then build around it.
Here are some examples on using foresight with Kaidan and SZ Prop.
This is another possible donation that you can do when you see stairs