A Nail, a small rod
a rod that sets the difference
between structure and collapse

One tip sharp to dig and impact
Dangerous alone without a guide
Ready to split and open a hard exterior
and grip into an ever impenetrable interior
To force an idea, a point

The other end flat for taking on a force needed to dig
Flat enough to focus the effort to force open and split
To forcibly separate and and guide dangers
To be the force behind the idea, the point

Using one's own hand to drive in
Damages the hand more than the exterior
Only brushing and leaving no mark

A hammer whether ball-peen, claw or mallet to drive in
May drive in the nail if hit just right
But miss and risk damaging the exterior
Only denting and bruising it

If you cannot seem to drive the nail
whether missing the flat end
or the material to impenetrable
you might be the need
of a sledgehammer