We use have + object + past participle when we talk about someone doing something for us that we ask or instruct them to do. It emphasises the process/action rather than who performs it.

Look at the example:

We're having the dinner delivered tonight. (They aren't going to deliver their dinner by themselves. Someone else is going to deliver it. The emphasis here is on the fact that they are having their dinner delivered rather than who is doing it).

We also can use have + object + past participle when something bad happens, especially when someone is affected by an action which they didn't cause.

Look at the example:

She has had her purse stolen. (She is affected by the action but she didn't cause this to happen. It's not her fault).

We can use get instead of have to form causative. Get is more common in spoken English.

Look at the example:

The students get their essays checked. The service delivered my dinner — (have / deliver) I had my dinner delivered.

1. Sarah took her car to the carwash.

   Sarah had her car washed at the carwash.

2. The hairdresser cut Tom's hair.

   Tom got his hair cut .

3. The maid is cleaning the window.

   I am having the window cleaned 'm having the window cleaned .

4. When I go on holiday, I ask my brother to walk my dog.

   I get my dog walked when I'm on holiday.

5. I asked the builders to repair the roof.

   I got the roof repaired .

6. The baker has just baked the cake for Mary.

   Mary has just had the cake baked 's just had the cake baked .