The phrase "a signpost that" is correct and usable in written English.
It can be used to indicate a clue or indication of something that follows or is related to the context being discussed.
Example: "The author uses a signpost that suggests the main theme of the story will revolve around redemption."
Alternatives: "an indicator that" or "a marker that".
It stood like a signpost that read "Slow" even as age and events whooshed me forward.
The picture on this article was changed on 8 May 2017 because the original was misleading in that it showed a signpost that did not contain Arabic text.
Even the fact that it is the "finger" of a signpost that points in the right direction, and not the other end of it, is something that you have to learn.
An undulating serpentine of aquamarine tile and seafoam-blue brick, the Summit Hotel opened in 1961 with Latin-themed restaurants and a signpost that looked like a flying saucer docking station made of Cadillac tail fins.
If you have children of a certain age chances are they have made a giant Pikachu out of yellow blocks or put up a signpost that says "Poop Here" next to a chicken pen.
Every feeling is a signpost that has the ability to lead us to growth and increasing self-awareness.
On this basis we deduced that the discs serve as way-marks, providing a portable signpost that enables the mouse to orient its movements around places of ephemeral interest.
Membership is also an important signpost that a country is on the way to achieving Western European standards of living, an important goal for a former Soviet republic like Estonia that has long been among the Baltic states eager to develop.
A high density of CCPs may be an economic signpost that health interventions are needed within a neighbourhood, including strategies that address the causes of premature death, such as intentional self-harm, poisoning and alcohol-related liver disease (see online supplementary table S1).
OpenCourseWare was an important signpost that hammered home the point that the content of a university course was being rapidly commoditized by technology.
But it is certainly a major new signpost that future performances and recordings will have to take into account.
