So we can now conclude that they can have an impact in practice and in theory. That being said, the exact circumstances in which balance sheet instruments are effective warrants some further detail. In the last decade many different types of balance sheet instruments have been implemented by central banks.
The literature tells us there is one feature that binds them: frictions in financial markets that imply imperfect asset substitutability or market segmentation. These frictions are crucial for these instruments to have an impact on financial conditions.