The Quasi-Steady Quasi-Homogeneous (QSQH) theory describes one of the mechanisms by which the large-scale motions active outside the viscous and buffer layers affect (‘modulate’) the turbulent flow inside these layers. The theory presumes that the near-wall turbulence adjusts itself to the large-scale component of the wall friction.  Formulated in a mathematically rigorous form, the theory allows nontrivial quantitative predictions. The talk will describe the basics the theory and its methods, its current state, and a new tool making the application of this theory easy. Examples of applications and comparisons will be given.