P{loxP(DH.0)} is a transgenic donor construct containing a codon phase 0 'Double Header' (DH) trapping cassette flanked by attB sites nested within a pair of loxP sites. Expression of P1cre recombinase will excise and circularise the DH cassette, which can then be integrated into the attP sites of a Mi{MIC} insertion using phiC31:int integrase. Integration of the cassette into a coding intron (with the same phase) of a native Drosophila gene of interest should result in the cassette trapping the gene, with the nature of the trap depending on the orientation in which the DH cassette is inserted relative to the direction of transcription of the native gene, since the DH cassette contains 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.