What are anchor bolt cages?

A number of anchor bolts / hold down bolts can be "caged" together so that critical measurements are maintained when the steel is cast into the concrete slab - which is important for dealing with prefabricated structural steel and such.

Typically, several anchor bolts / hold down bolts are connected by steel bracing and the assembles "cage" is welded together.

See this link: http://www.damsteel.com.au/products/caged.html

Hope this helps.