"act as guards" is correct and usable in written English.
You could use it in a sentence such as, "The security personnel acted as guards to protect the premises."
Individuals were much more likely to act as guards if they had just been fed by the researchers than if they were hungry.
"It was reminiscent of the kapo in the fascist camps," Mr. Borshov said of empowering some prisoners to act as guards.
The Perrygrove steam train trundles along a single track, stopping to let its junior passengers act as guards and wave the flag, while Puzzlewood is a maze of paths running through mossy, Tolkeinesque woods.
They act as guards of honour at some Government House functions and attended the restoration opening of the Albany, Western Australia fort, and the annual re-enactment of the Battle of Waterloo in Keyneton, Victoria.
The pleurocystidia protrude from the face of the gill and act as guards, preventing adjacent gills from touching each other, and also ensuring that the basidia and spores have sufficient room for development.
And even the brightest spots in the Marvel and DC catalogs don't feature characters as nuanced and interesting as the ones seen in T'Challa's homeland, where muscular women are heroes, warring with other nations is not the answer, armored rhinos act as guards and everyone's attire glitters so spectacularly it might as well have catwalked straight off a Wakanda Fashion Week runway.
The view of the Republican leadership is that -- in addition to defeating President Obama -- their principal mission is to act as guard dogs for the exploding incomes of the top 1%.
The existence in different rat cells of a perinuclear multi-enzyme structure mainly formed by selected cationic proteins including key protection enzymes (Figure 3 and Table 2) indicates that this particular region may act as guard against oxidative damage.
Sixteen soldiers of the Royal Nova Scotia Regiment acted as guards for the hospital beginning in 1796.
As a result, the ARF leadership decided to defend Armenian churches by dispatching militiamen who acted as guards and by holding mass demonstrations.
Increasing evidence suggests that resident microbiomes act more as guards than guests, in consideration of the benefits to the host.
