There are various items that are generally not allowed to be carried in your suitcase during a flight. These items can vary depending on the specific rules and regulations of the airline and the country you are traveling to. Here are some common items that are usually not allowed in checked baggage:

1. Flammable substances and items, such as fuel, flammable liquids, and aerosol cans.

2. Explosive materials, including fireworks, caps, and explosives.

3. Toxic substances and corrosive materials, such as acids, pesticides, and bleaches.

4. Sharp objects, like knives, scissors, nail files, and screwdrivers.

5. Weapons and firearms, including replica weapons and ammunition.

6. Large quantities of batteries, especially lithium batteries.

7. Drugs and illegal substances.

It's important to always check the guidelines of your specific airline and the restrictions of the destination country before traveling. These rules can vary, so it's wise to prepare well and remove any prohibited items from your checked baggage to avoid problems at the airport.