The sonic trowel was a sonic device owned by River Song, shaped like a regular trowel. It could fire an energy beam similar to that of a sonic blaster.
River used the trowel to stun King Hydroflax's warrior monk bodyguards, though it was ineffective against Hydroflax's robot body. The Twelfth Doctor considered the trowel "just embarrassing" and gave River a sonic screwdriver of her own. (TV: The Husbands of River Song)