Packing a carry-on seems pretty straightforward until you start trying to fit everything you need into one small bag. Then there are airport security rules to think about. An item you’ve carried around for years may suddenly become a problem at the checkpoint simply because you forgot it was tucked into a side pocket.

A little planning before leaving home can save you from throwing things away, repacking your bag, or holding up the security line. If you want to keep your carry-on useful and avoid common packing mistakes, here are eight things worth leaving out.

Flammable Products

Certain flammable products aren’t allowed in carry-on luggage, and the rules can apply to more items than travelers expect. Fuels, some aerosols, and other flammable substances may be restricted or prohibited depending on the product and how it’s packaged.

A small container doesn’t automatically make a restricted item acceptable. Check the current TSA rules before packing anything that contains flammable material.

Firearms, Knives, and Other Weapons

Weapons and certain self-defense items don’t belong in your carry-on. Firearms, ammunition, knives, stun guns, and pepper spray can be subject to strict transportation rules, and some items are prohibited in the cabin altogether.

It’s surprisingly easy to forget about a pocketknife or multi-tool tucked into a backpack you use every day. Before heading to the airport, check every pocket and compartment.

If you’re traveling with a firearm, TSA generally requires it to be unloaded, locked in a hard-sided container, transported in checked baggage, and declared to the airline. State and local laws can also apply, so check the rules for your departure and arrival locations before traveling.

Oversized Bottles of Liquids

That full-size bottle of shampoo might seem harmless, especially if there’s only a little left inside. Airport security looks at the size of the container, though, rather than how much liquid remains.

For flights departing from U.S. airports, TSA’s 3-1-1 liquids rule generally limits carry-on liquids, gels, aerosols, creams, and pastes to containers holding 3.4 ounces (100 milliliters) or less. These containers must fit into one quart-size bag.

Transfer toiletries into smaller travel containers or pack larger bottles in checked luggage.

Bulky Winter Jackets

A thick winter coat can take up a surprising amount of room inside a carry-on. If you’re trying to fit clothes, toiletries, electronics, and other necessities into a small bag, that coat can eat up valuable space.

Wearing your jacket through the airport is usually much easier. You can take it off during the flight and keep it with you rather than stuffing it into your luggage.

Full-Size Travel Pillows

A large travel pillow can be comfortable, but it can also become an awkward piece of luggage on an already crowded travel day.

Inflatable pillows are easier to pack because they can be deflated and tucked into a small pocket when you’re finished using them. A compressible pillow is another option if you prefer something softer.

Hair Dryers and Bulky Styling Tools

Hair dryers, curling irons, straighteners, and other styling tools can take up a lot of room. For a short trip, packing several large tools may leave you with less space for things you’ll actually use.

Before packing one, check whether your hotel, rental, or other accommodation already provides a hair dryer. You may be able to leave it at home and free up some room in your bag.

Gifts That Need Wrapping

Wrapped presents can create an unnecessary headache at airport security. If a security officer needs to inspect the contents, the wrapping may have to be removed.

If you’re carrying gifts, leave them unwrapped until you reach your destination. You can bring wrapping supplies separately or wrap everything after you arrive. It takes a little planning, but it can save you from having a carefully wrapped present opened at the checkpoint.

Large Food Containers

Some foods don’t look like liquids, but TSA treats certain soft or spreadable foods like liquids or gels for screening purposes.

Peanut butter, yogurt, dips, gravy, sauces, and soft cheeses can fall under the liquids rule. A container larger than the permitted amount may not make it through security, even if you only have a small amount left inside.

Solid foods such as sandwiches, baked goods, and many snacks are generally easier to pack in a carry-on. If you’re unsure about a particular food, check the current TSA guidance before putting it in your bag.

A few minutes spent checking your carry-on before leaving home can save you from unpacking everything at the security checkpoint. Keep liquids within the allowed limits, check those forgotten pockets for prohibited items, and leave bulky extras behind whenever you can.