panel by Historic Scotland tells us....
"You are standing inside the Broch, having come through
the narrow entrance passage. Partway down the passage can
be seen the setting for a wooden door-frame and the holes
for a stout bar behind it. Within the door is the entrance
to a chamber where a guard or a watchdog might have been stationed.
We do not know why the guard cell here at Dun Troddan is on
the legt, and at Dun Telve on the right.
An inner entrance leads to a stair curving up between the
inner and outer face of a hollow, galleried wall. The narrowing
of the walls at their highest level suggests the stair may
not have reached right to the top. Gaps
in the stonework of the inner wallface were probably
lighten the mass of masonry rather than to allow light into
The stone ruins, even if imagined complete and standing over
10 m tall, are only half of the story. Modern excavators found
holes for stout wooden posts in the floor, hinting at a now
vanished, raised floor platform, or possibly even two, covered
by a sloping roof, with a central hole for letting light in
and smoke out. A ledge high on the inner wallface may have
carried the outer edge of such a structure.
It seems likely that the inhabitants lived in reasonable comfort
in this wooden structure rather than in the cramped, damp
and murky galleries within the stone walls, these being used
for storage. The stone stairway, too, may have been unimportant
in daily life, with access to the upper levels and wallhead
by wooden ladders.
Even as partly ruined structures, the brochs of Glenelg bear
witness to the ingenuity of Scotland's Iron Age farmers faced
with a threat whose nature we can only guess at."