The Absolute Phrase
Recognize an absolute phrase when you see one.
Noun + Participle + Optional Modifier(s) and/or Object(s)
Here are some examples:
Legs = noun; quivering = participle.
Her arms folded across her chest
Arms = noun; folded = participle; her, across her chest = modifiers.
Their fingers scraping the leftover frosting off the plates
Fingers = noun; scraping = participle; frosting = direct object; their, the, leftover, off the plates = modifiers.
Rather than modifying a specific word, an absolute phrase will describe the whole clause:
Legs quivering, our old dog Gizmo dreamed of chasing squirrels.
Her arms folded across her chest, Professor Hill warned the class about the penalties of plagiarism.
The family devoured Aunt Lenora's carrot cake, their fingers scraping the leftover frosting from the plates.
Legs quivering, for example, describes not only Gizmo but also the manner of this sleep. Her arms folded across her chest helps us picture both Professor Hill and the severity of her warning. Their fingers scraping the leftover frosting from the plates lets us see this one family and the degree of their hunger.