Simple answer - don’t bother trying. Yes it is possible to lock your tent from inside or outside by using small padlocks, which can go through the zip loops on the tent internally or externally.

Some people like to do this before they go to sleep so they know their tent is safe from intruders.

However, it is a bad idea in my opinion:

Here’s Why?

1. The thief may damage the tent to force entry.
2. The thief may slash the tent with a knife to gain entry.
3. Locking the tent shows you have items of value inside. 
4. Locking the tent whilst your inside, is a fire risk. Tents can be flammable, and you just never know, or want to hinder an escape if there was a fire.

Why you might wish to lock your tent:

1. Festivals - can be rife with theft - especially cash or alcohol.
2. To keep valuables safe.
3. To stop anyone entering to nosy through your items.
4. To stop anyone entering whilst you sleep.

Alternate Options to Locking your Family Tent

1. Anything of value - lock them away in the car out of sight.
2. Don’t take anything you cannot afford to lose.
3. Make sure you have insurance on valuable items.

Alternate Options to Locking your tent if on a Festival:

1. Safety boxes - there are usually security centres on each festival, whereby you can get a locker free of charge, to keep your items safe.
2. Don’t take anything you cannot afford to lose.
3. Don't keep bags or wallets or anything of this sort near the tent doors, as often thiefs will poke their hand through the open zip and grab anything in reach whilst you are sleeping.
4. Take an older / spare phone, so it does not matter if you lose it.
5. Keep your valuables close by or safe.
6. Sleep with your phone or valuables tucked at the bottom of your sleeping bag, if you cannot lock them away in a safe area.
7. Don’t take too much cash, as all festivals accept debit or credit card now.
8. Take a smaller tent as larger, standing height tents are harder to secure.
9. Use a tripwire alarm, these are effective alarms, which work on a tripwire, and can provide a loud alarm. Ideal if you are worried about someone entering the tent whilst you are asleep as it will scare them away.