Your dog has a sock under the table. When you walk toward them they speed up their chewing, turn their body away, and freeze as your hand comes down.
This is the one article in the Library that spends most of its length on what not to do. It also says when to stop reading and call someone.
Safety note
If your dog has growled, snapped, lunged or bitten over an object, food, a bed or a person, stop here and read Get help now. Guarding that has already involved teeth needs a person who can see your dog. Nothing on this page is a substitute for that.
What guarding is
Holding on to something valuable is ordinary dog behaviour. It becomes more visible in adolescence, as your dog gets faster, taller and better at finding things worth keeping.
The behaviour has a sequence: eat faster, turn away, freeze, hard stare, growl. The early parts of that sequence are information, and they are the part you want to keep.
Four things to stop today
Stop taking things out of your dog's mouth with your hand. Every removal teaches that your approach means loss, which is what builds the growl.
Stop the practice of putting your hand in their bowl or taking food away to prove something. Punishment-based approaches are associated with fear, avoidance and defensive aggression.
Stop cornering. A dog under a table with something valuable has no exit, and no exit is where a bite becomes the remaining option.
Stop leaving the good stuff available. Socks, tea towels, shoes and food packaging in reach are rehearsals you did not need to give them.
The trade, and how to practise it before you need it
Practise with items your dog does not care about, at a time when nothing is stolen. The trade has to be an old habit by the time a real sock is involved.
Give your dog a boring item, like a rolled sock they have never had. Let them hold it.
From 6 feet away, say one cheerful word, then scatter 5 treats on the floor away from them. Do not walk toward the item.
While your dog eats, pick the item up calmly and walk away. Repeat 5 times, then stop for the day.
Reward-based methods are what the veterinary behaviour guidance recommends, and behaviour change is built from management plus reinforcement. Both of those apply here more than anywhere else.
In the moment, when they already have something
Decide whether the item is dangerous. A cooked bone, a corn cob, a razor, medication or anything that could block or cut needs a veterinarian, not a training decision.
If it is harmless, walk away and open the fridge. Most adolescent dogs follow food and drop the item on the way.
If it is dangerous and your dog will not trade, call your veterinary practice and tell them what your dog has. Do not force it out of their mouth.
Why we will not sell you a technique for this
Guarding is where quick-fix advice does the most damage. A review of aversive training methods found them associated with worse welfare outcomes and no training advantage.
Dogs trained with aversive methods showed more stress-related behaviour than dogs trained with rewards. A dog who has learned that growling gets punished may skip the growl next time.
Today's version, in one line: pick up the socks, and practise the trade with an item nobody wants.