So far, when we created brushes, we created blocks defined by an imaginary cube in 3D space. Hammer's default brush type is the block. But this can be changed by modifying the Objects property of the Object Toolbar.
Click on the objects drop-down field to select either the arch, block, cylinder, torus (donut), sphere, spike, or a wedge object.
Cylinders are created by selecting cylinder from the Objects drop-down list. They're created just like boxes are except you specify how many sides you would like the cylinder to have.
Upon creation, the top of the cylinder will face up, aligned with the z axis. This means that you will need to rotate the object to be in the final position you wanted. You can change which direction the object originally faces in the options menu. Navigate to Tools | Options | 2D Views and select the Reorient primitives on creation in the active 2D view option.
Cylinders, cones, arches, and tori will now face the active 2D view when created...