Making a gun that can fire building blocks is an interesting manual activity, but please note that safety is always the primary consideration. Make sure you don't hurt yourself or others, and treat it as pure entertainment. The following is a simple tutorial for building a building block gun:

Materials required:

1. A strong rectangular cardboard (about 20x30)

2. Plastic straws

sellotape

scissors

5. Building blocks

Steps:

1. Preparing cardboard: Cut rectangular cardboard into appropriate sizes to make the main body of the gun. You can choose the color of the cardboard according to your preference.

2. Making the gun body: roll the cardboard into a tube with the same diameter as the plastic straw. Make sure it is strong enough to support the straw. Fix the cardboard into a tube with adhesive tape to ensure that it will not loosen.

3. Installing a straw: Insert a plastic straw into one end of the gun body to make it a gun body. Make sure that the straw matches the bottom of the cardboard. Fix the straw firmly on the gun body with adhesive tape to ensure that it will not slip out.

4. Making the trigger: cut a small piece from the cardboard, about 5x5cm in size. This will be the fuse. Fix the trigger on the gun body with adhesive tape and ensure that it can move freely.

5. Test the function of the gun: put a building block at one end of the barrel, and then gently pull the trigger. Building blocks should be ejected. If it doesn't work, check whether the straw is installed correctly and whether the trigger moves freely.

6. Loading and launching: put the building blocks into the barrel, and then gently pull the trigger. Building blocks should be ejected. Please be careful not to shoot the building blocks at others or fragile objects.

Making a building block gun may be an interesting manual activity, but please make sure it is carried out in a safe environment and educate children not to use it to hurt others. Please supervise the children's activities at all times to ensure their safety.