These stinging cell animalsuse what
to move their armlike parts?

Cnidarians uses arm-like parts called tentacles to sting.

Explanation:

Animals belonging to genus Cnidaria use arm-like structures called tentacles to sting. The cnidarians tentacles are present with specialized stinging cells called cnidocytes.

These cnidocytes are responsible for the stinging action which is done by the cnidocyte organelle called the nematocysts or the stingers.

Nemotocyts contain coiled thread or barb-like or hair-like structures which fires the toxin out while stinging.

The opening or the mouth-like parts on the tentacles contain numerous cnidocytes which releases toxin when the tentacles are touched by another organism or when the cnindarian touches its prey.

equal distribution i think.