A whomper is a large, flat steel blade (about 20"X14") attached to a steel pipe about 4 feet long.. the idea is to slam the thing into the ground and rock it back and forth as you go along making your trench line. They are not "sprinkler friendly" and suck in sand, gravel or rooted areas. I've installed in Fla for 17 yrs and NEVER used one.
This is CABL.com posting #139689. Tiny Link: cabl.co/mKvd