The floor was some species of concrete, perfectly flat and smooth.

An easel is used to hold the paper perfectly flat.

Her eyes had different depths, sometimes they seemed perfectly flat.

Yet they never came to the hill: the tunnel remained perfectly flat.

Don't be over-concerned if the ground in front of you doesn't seem perfectly flat.

The picture went perfectly flat although remaining a fine photograph.

A perfectly flat screen will usually give you the best picture.

By looking at any surface on the microscopic level, one would find that it is never perfectly flat.

He'd no longer have a perfectly flat tax, but it would nonetheless work beautifully.

"I have my orders," he said, his voice perfectly flat and even.