hold (something) steady
When something is "steady", it means that it's not changing a lot. For example:
They seem to have a steady relationship.
The stock market has been steady this week.
Be careful stepping on that. It's not steady.
So "holding ___ steady" means holding it so that it doesn't move around. You can hold a ladder steady, a stool that someone is standing on, a piece of wood that you're nailing, etc.
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