Of VERY Little Value

I grew up with some phrases that denoted that "something" was of very little or no value:

"Not worth a Tinker's Dam": Tinker's-dam - a wall of dough raised around a place which a plumber desires to flood with a coat of solder. The dam material is a single use, once used it is thrown away as worthless." Tinkers used to travel offering to mend: pots, pans, utensils, sharpen knives and scissors

"Not worth a Dam": A dam was a small Indian copper coin of very little monetary value.

"Not worth the Candle": Not worth the necessary effort, cost, or trouble. Also alludes to gambling by candlelight, which involved the expense of illumination. If the winnings were not sufficient, they did not warrant the expense.