The Inner and Outer Guards are the Lodge's 'doormen', as it were, making sure that only those who are entitled to enter the Lodge are able to do so. The Outer Guard is known in the Lodge as the Tyler.
The Inner Guard is one of the more junior offices within the Lodge; nevertheless, it is still an important one.
The main purpose of having an Inner Guard is to ensure that the entrance within the Lodge is duly guarded against admittance of non-masons or intruders should they get past the Tyler. This is achieved by maintaining the door in a locked position and only responding to reports that are given in the correct manner. Entrance is only allowed once the correct colloquy has been exchanged.
The Inner Guard is the first member of within the Lodge rooms to respond to the Tyler. This, in effect, starts all ceremonies and is important that it is completed correctly, firstly to settle everyone into what they are about to do and secondly to confirm candidates are prepared properly and in possession of the correct passwords to enter the Lodge.
Generally, by starting the ceremony correctly, the Tyler and Inner Guard encourage the rest of the ceremony to progress smoothly.