This part is associated with Tn5 transposon devices
Tn5 transposase is a popular enzyme that generates protein-DNA complexes called transposomes from DNAs flanked by "terminal repeats". These terminal repeats, or TR's, are specific cis elements. The transposomes are highly reactive and insert the DNA contained within them randomly into other DNAs (such as a genome). Unlike Sleeping Beauty and piggyBac which comes from eukaryotic organisms, Tn5 comes from enterobacterial tranposons.
You should read the following papers
References: PMID 12189420, PMID 16079303, PMID 18805998