A scarce species that in the field closely resembles Dicranella heteromalla and Ditrichum heteromallum, especially when capsules are absent. Take a look at the leaves with a lens, however and two features should become apparent. First of all, the leaf bases sheath the stems and if you manage to pull one off intact, you’ll see that the basal portion of the leaf looks more or less rectangular before abruptly contracting into the portion that curves away from the stem. This is the second useful feature – the upper part of the leaf is long, narrow and channelled (lens). The nerve is not as strong as Dicranella heteromalla but is more distinct than Ditrichum heteromallum. Neither species has a rectangular-looking sheathing leaf base.
Fortunately, plants often have capsules which makes identification easier. They are held on a long, purple to red seta (D. heteromalla is yellow, at least when young) and are usually furrowed.
It’s always best to check candidate material of this plant under the microscope unless you are very familiar with it.