running iron

running iron (plural running irons)

1. A branding iron which is not bent into the shape of the mark but rather requires the user to write the desired brand (and thus allows writing any brand).
   • 2007, Philip Ashton Rollins, The Cowboy, page 183:

     So flagrantly did these gentlemen miswield the “running iron,” that several States eventually forbade its use by anybody, and everywhere its mere possession gave rise to suspicion.