A point mass particle $m$ will rest on incline if incline angle $\theta$ satisfies
$$\tag{1} \tan\theta \le \mu, $$
where $\mu = \mu_s$ is static friction between point mass and the incline surface.
- -, “A particle on an inclined plane”, in Mechanics, Academic Skills Kit, Newcastle University, 2022, url https://www.ncl.ac.uk/webtemplate/ask-assets/external/maths-resources/mechanics/dynamics/inclined-planes-mechanics.html [20221129].