Originally Posted by
MSPeconomist
Once upon a time, the standard hotel reservation in the USA (not including certain big city hotels or resorts, which tended to require deposits far in advance) would be held only until 4 or 6 pm, although one could almost certainly call in the afternoon to advise the front desk of a letter arrival.
They used to hold your room until 4 or 6 without a credit card. If you wanted it held later, you needed to "guarantee" your reservation.