The tables were of the cheap, light metals so common on the spacer-supplied worlds of the Edge, and they wobbled.
"Warlord of Kor"
Terry Gene Carr
The jack guides are built up of spacer blocks held together by thin strips along the sides.
"Italian Harpsichord-Building in the 16th and 17th Centuries"
John D. Shortridge
The spacer ground to an agonized stop.
"Master of the Moondog"
Stanley Mullen