Pantographs

noun

1. A mechanical linkage based on parallelograms causing two objects to move in parallel; notably as a drawing aid.

   "A pantograph can be adjusted to make either scaled or exact copies."

2. By extension, a structure of crosswise bars linked in such a way that it can extend and compress like an accordion, such as in a pantograph mirror or a scissor lift.
3. A pattern printed on a document to reduce the ease of photocopying.

   "I was impressed by the quality of the pantograph; I hadn't noticed it on the original, but the copies were covered in unpleasant lines."

4. A similarly-formed conductive device, now usually Z-shaped, that collects electric current from overhead lines for trains and trams.