This article is from the RSC/UKSC Cricket FAQ, by Ganesh with numerous contributions by others.
In a first-class match, a tail-ender sent in when a wicket falls
near the end of a day's play. The theory is that a batsman is
most vulnerable at the start of his innings and early in the day,
so this tactic is intended to protect a specialist batsman from
one of these dangerous times.
 
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