homework and exercises - Determine direction of friction on a block held stationary against a vertical wall

A block of mass $m$ is pushed up against a wall and held stationary by a force $ F$ that makes an acute angle $\theta $ with the horizontal.

May I know how to determine the direction of the static friction $f_s$?

Friction exerted by wall on the block acts in the opposite direction of the impending motion (or motion) of the block relative to wall. In absence of $F$ and $f_s$, the object will move vertically downwards. ($F$ is required to keep the block in contact with the wall) So $f_s$ acts vertically upwards? Should we assume that the block can only move parallel to the wall?

Please advise on my doubts. Thank you.