bar of soap 

Something very plain and boring looking.
Usually said when describing a group of the object.

Example, if there's a whole lot of bikes all together and you can't tell the difference you would say:

"I can't tell one another from a bar of soap."

bar of soap by McGoonster October 5, 2009

a bar of soap 

The term "a bar of soap" is an expression used to describe an individual who is very fickle; you can never keep hold of them for very long without them slipping out of your hands. Typically given for a person who is overtly avoidant.

Henry's always changing his mind last minute, he's such a bar of soap.

a bar of soap by sgrove88888 September 8, 2025

About as useful as a dry bar of soap

Useless.

"Cba"

"You're about as useful as a dry bar of soap"

About as useful as a dry bar of soap by T4Y March 30, 2022