Modify > Extrude > Extrude Shells to Bricks prompts you with the following dialog.
It generates a series of bricks by extruding selected shells along a global direction. You may specify a distance list and an extrusion direction for the generation of shells. The extrusion direction must not be parallel to the selected shells. You have the option to automatically merge nodes and elements after extrusion. You should check this option unless duplicate nodes are explicitly permitted. You also have the option to automatically delete selected shells after the extrusion.
The input in the above dialog is applied to the shells in the screen capture below...
shells used for extruding
...to generate the bricks in the following screen capture by extruding.
bricks generated