What is .DRU file extension?
File created by CadSoft EAGLE, an application used for designing Printed Circuit Boards (PCB); contains design rules for manufacturing a PCB; includes settings for layers, distances, size, shapes, masks, and clearance.
NOTE: EAGLE is short for "Easily Applicable Graphical Layout Editor."
You can see a list of software programs here on www.easyfileopener.org that can open this file type so that you don’t need to search for it on the web. You can then open your file with this extension using a software listed below.