The notion of D-sublocale is explored. This is the notion analogue to that of sublocale in the duality of T D -spaces. A sublocale S of a frame L is a D-sublocale if and only if the corresponding localic map preserves the property of being a covered prime. It is shown that for a frame L the system of those sublocales which are also D-sublocales form a dense sublocale S D (L) of the coframe S(L) of all its sublocales. It is also shown that the spatialization sp D [S D (L)] of S D (L) consists precisely of those D-sublocales of L which are T D -spatial. Additionally, frames such that we have S D (L) ∼ = P(pt D (L)) -that is, those such that D-sublocales perfectly represent subspaces -are characterized as those T D -spatial frames such that S D (L) is the Booleanization of S(L).