Working with Apply for rules - tcp ports example ============================================== This example wants to show you how to make use of `Apply For` rule for services. First you need to define a `tcp_ports` data field of type `Array` assigned to a `Host Template`. Refer to [Working with fields](14-Fields-example-interfaces-array.md) section to setup a data field. You also need to define a `tcp_port` data field of type `String`, we will associate it to a `Service Template` later. Then, please go to the `Dashboard` and choose the `Monitored services` dashlet:  Then create a new `Service template` with check command `tcp`:  Then associate the data field `tcp_port` to this `Service template`:  Then create a new `apply-rule` for the `Service template`:  Now define the `Apply For` property, select the previously defined field `tcp_ports` associated to the host template. `Apply For` rule define a variable `config` that can be used as `$config$`, it corresponds to the item of the array it will iterate on. Set the `Tcp port` property to `$config$`:  (Side note: if you can't see your `tcp_ports` property in `Apply For` dropdown, try to create one host with a non-empty `tcp_ports` value.) That's it, now all your hosts defining a `tcp_ports` variable will be assigned the `Tcp Check` service. Have a look at the config preview, it will show you how `Apply For` services will look like once deployed: