The Grail psalms, which are used in the English Liturgy of the Hours, are designed with a given number of stresses in each line. The number of syllables per line may vary from one verse to the next, but the stress pattern remains consistent throughout the psalm. As one might say:
When chánting each psálm,
the páttern of stréss is consístent.
If you lóok at the márks,
you will sée how the psálm should be chánted.
In general, among the printed Liturgy of the Hours books, the English books tend to include these marks (“pointing”) and the American ones tend not to. The latest versions of Universalis give you a choice between viewing the stress marks (if they are helpful) or hiding them (if they are distracting).
The question then arises – what to do with these marks once you have them?