In this paper, I argue that hinge propositions are ways of acting that constitute abilities or skills. My starting point is Moyal-Sharrock's account of hinge propositions. However, Moyal-Sharrock's account leaves gaps to be filled, as it does not offer a unified explanation of the origin of our ungrounded grounds. Her account also lacks resources to respond to the issue of demarcation, since it does not provide a criterion for distinguishing ways of acting that can legitimately fulfill the role of ungrounded grounds from those that cannot. Without an answer to this issue, the relativistic threat is serious. I then propose that by narrowing the ways of acting to those that are constitutive of abilities, we can deal with the relativistic thr...