TI{DH.0} represents a DNA segment which contains a 'Double Header' (DH) cassette designed to efficiently trap genes when inserted in a codon phase 0 coding intron, and which has been inserted into the genome via any technique (such as CRISPR/Cas9 or other targeted mutagenesis) that results in the inserted DNA not being flanked by transposable element ends. The DH cassette comprises two independent trapping modules oriented in opposite directions: 1. a protein-trap (PT) module for tagging endogenous proteins, composed of a splice acceptor site, a EGFP-Tag:CALI(TC)-Tag:StrepII-Tag:CS(TEVp)-3xTag:FLAG multi-tag cassette and a splice donor site, and 2: a gene-trap (GT) module designed to truncate the endogenous gene into which it inserts, as it contains T2A-GAL4 followed by a polyadenylation signal. Translation should skip at the T2A sequence, truncating the endogenous protein and producing a separate GAL4 protein. Both of the modules are in codon phase 0. Depending on the orientation in which the DH cassette is inserted into the coding intron relative to the direction of transcription of the endogenous gene, the inserted TI{DH.0} element can either be in the 'protein-trap' or 'gene-trap' orientation for that gene.