*this is the tool he is using in the picture. It is called a "groma" in English too.
Castra sunt in formāquadrae. Castra quattuor portās habent. Castra multa tentōria habent. Octō mīlitēs in ūnō tentōriō habitant. Nocte, duō mīlitēs prope portās castra custōdiunt et sex mīlitēs in tentōriō dormiunt.