I've never been spanked with a razor strop, my dad didn't have one. Is it worse than the belt?
~ Andrew Finklehouse
A razor strop is a leather strap, just like a belt. The strop, however, is wider and thicker (and therefore, heavier) than any normal belt.
Of course, the impact of any leather strap, when used to tan a bare bottom, depends mostly upon 1> the force with which the disciplinarian applies the correction, and 2> the number of swats applied. Having said this, a strop (because it is wider, thicker, and heavier), certainly has the potential to deliver a more severe thrashing than any typical belt.
A razor strop, when used for discipline, is very similar to the Louisiana prison strap, the Texas prison strap, and the Canadian prison strap. Sometimes, judges would sentence men to receive disciplinary sessions with these straps while incarcerated for their crimes. Prison wardens also had the authority to administer the strap to correct a prisoners' misbehaviors during incarceration. Although they are no longer in use, these prison straps are legendary for their effective correction of adult male misbehaviors.
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When used domestically, for family discipline, a razor strop must be used very responsibly. My father had a relatively short/thin/light leather strap that he used on my sisters and me when we were in grade/elementary school. When I entered junior high school, my father started tanning my hide with the razor strop, when necessary. He only used the strop on my sisters a few times, when he felt that they really deserved it.