We can sometimes use for + ing to talk about the purpose of a thing. When we do, it means the same asto + infinitive.
- What is that for? It is for opening envelopes
- This bell is for calling the waiter.
- This bell is to call the waiter.
When we talk about the purpose of somebody's actions, we cannot use for + ing.
- I went there to ask for help.
- You will have to queue a long time. to get tickets.
However, it is sometimes possible to use for + noun for this.
- I went there for help.
- You will have to queue a lo