The top half of the cap is a hollow cavity with a dubious pinhole at its center.
From the denverpost.com
Bring your eye close to it and look through the pinhole as you rotate the card.
From the newscientist.com
We use three methods to ensure that our silica shells are, in fact, pinhole free.
From the nature.com
Poke a pinhole in the center of a piece of paper or borrow blinders from Zenyatta.
From the ocregister.com
Far from the pinhole the emerging spherical wavefronts are approximately flat.
From the en.wikipedia.org
Perhaps we should watch these games through a pinhole camera, like an eclipse.
From the washingtonpost.com
The first glass insulators used in large quantities had an unthreaded pinhole.
From the en.wikipedia.org
With too small a pinhole the sharpness again becomes worse due to diffraction.
From the en.wikipedia.org
He hunts them down and fixes them to a point using pinhole photography and collage.
From the independent.co.uk
More examples
A small puncture that might have been made by a pin
The Dead 60s were an English ska punk band from Liverpool. The band's sound is a mixture of punk rock, ska, dub and reggae. They have taken influences from artists such as King Tubby, Jackie Mittoo, Gang of Four and A Certain Ratio.
(pinholes) Tiny, unsealed spots in the nonprinting areas of a screen, which allow ink to flow onto areas that aren't supposed to be printed.
(Pinholes) Small holes on the exposed gel coated surface that are about the diameter of common pins and may be easily counted.
(Pinholes) Microscopic imperfection of the coatings, that is, microscopic bare spots, also microscopic holes penetrating through a layer or thickness of light gage metal.
(Pinholes) Imperfections in the surface of a ceramic body/glaze.
(Pinholes) Small defects in finish film caused by surface contamination. Resembles tiny holes in the finish.
(Pinholes) Tiny holes in the emulsion of negatives or printing plates.
(Pinholes) A defect in the glaze caused by dust, firing too rapidly, or applying glaze to greenware.