Abstract: A modular crawler system for moving heavy objects comprises multiple crawlers that can be controlled independently of each other. Each crawler has a pair of tracks that are controllable independently of each other to enable the crawler to travel in straight lines as well as to turn the crawler. The crawlers are very compact and have low profiles. Each crawler has a carrier on which the object is placed. Locking means selectively engage and disengage the carrier. When the locking means is engaged with the carrier, the carrier cannot rotate within the crawler, thereby enabling multiple crawlers to move the object in a straight line. When the locking means is disengaged, the carrier can rotate relative to the object and thereby enable the crawler to turn under the object. The crawlers can then move the object in a different direction without changing the orientation of the object.