Okay, so we might have discussed present participial phrases here a time or two. (cough 19 cough) Now we'll talk about past participial phrases, which are exactly the same as present participial phrases except they use past participles instead of present participles.
Both forms can be used to conjugate verbs. The present form can be used as a noun (technically, a gerund). And both can be used as adjectives.
Evaluating the competition, the coach looked worried.
Evaluated for speed, the other team posted record times.
In both examples, the introductory phrases -- adjectives, remember -- modify the nouns they go next to. Because that's what we do with modifiers. We put them next to the words they modify.
Just like a present participial phrase, a past participial phrase can be misplaced:
The other team ate sandwiches, evaluated for speed.
This implies the sandwiches are evaluated for speed. It is a misplaced modifier because it has not been placed next to the word it modifies.
The sandwiches had too much mustard, evaluated for speed.
This is a dangling modifier because it cannot attach to any noun in that sentence. Neither the sandwiches nor the mustard are being evaluated for speed.
And if you think those examples look bizarre and funny, well, they are meant to. But so will every other botched PPP once you learn to spot this kind of error.