How to dig a moat?

[Kraken]

Playing this game again twenty years later. Just as fun as I remember. I am on combat mission 11 - killed the Rat and about half way through the Snake counties.

I am learning it all over again and am unsure how to dig.
I read there is a shovel icon in the build Castle tab under the Gatehouses section?
I see no shovel there or anywhere else in any build tab.
What am I missing?

[Abnormal Cybran]

I dont know when it unlocks in the campaign but you draw where you want the moat under the gatehouses tab then select engineers and/or low level military units such as spearmen and maces then click them to where you drew the moat. Draw bridges can also be placed before the moat is built so that will save some time too.

[Kraken]

There was one mission before the one Im on that explained Gatehouses and drawbridges. There were guys already filling in a moat. Maybe it didnt just fully unlock yet.

[Abnormal Cybran]

I havent gotten that far in the campaign yet, I found it while messing around in free build or the mission you are on just doesnt allow moats, like how a few of the earlier ones wont let you build hunters huts even though there are deer on the map

[Kraken]

Okay, yeah its the next mission when moats unlock. Weird bc they tell you how to do it in the mission prior, but then dont allow you to