A verb appearing as G. thlid- “to sort out, sift, sieve, discriminate” in the Gnomish Lexicon of the 1910s derived the early root ᴱ√SḶTḶ (GL/73; QL/84).
Neo-Sindarin: I would adapt this Gnomish verb as ᴺS. lhid- “to sort out, sift, sieve, discriminate” based on a neo-root ᴺ√SILIT, since in Tolkien later Sindarin phonology, initial sl became lh rather than thl.
A noun appearing as G. thlid “sieve” in the Gnomish Lexicon of the 1910s derived the early root ᴱ√SḶTḶ (GL/73; QL/84).
Neo-Sindarin: I would adapt this Gnomish verb as ᴺS. lhîd “sieve” based on a neo-root ᴺ√SILIT, since in Tolkien later Sindarin phonology, initial sl became lh rather than thl.