Well, a trap is just that.  It passes frequencies below the resonant
length of the trap, but stops signals at the resonant frequency.  I
am surprised that a tuner can't tune the very high swr two half wave
elements, but automatic tuners don't have the range I have become
accustomed to.  You will need a grid dip meeter to make sure the
traps are resonant.  Maybe their is a more modern way to do that to.