A rockery trowel is a hand trowel with a thinner
blade. It is used in areas where there isn't enough room for
a regular width hand trowel and indeed in rockery areas. (rock gardens,
alpine gardens) The thinner blade allows it to pry out soil
in smaller spaces (between rocks for example) so that small plants can
be inserted into these crevices.
Most Important Tip
If you do rock gardening, this is a great little tool but buy the most
expensive one you can find.
Cheaper units break quickly when you're prying rocks, jamming them into
crevices and your hands won't appreciate the cheaper, lighter tools.