A hollow chisel mortiser consists of a metal frame, a motor that rides up and down the frame via an articulating handle, and a chuck to which a mortising bit is attached. If you work primarily with mortises up to 5/8″, a 1/2 HP motor will suffice – otherwise opt for a 1 HP model. Features to look for include: a large work table (some have side extensions to better support long stock); a solid fence that is square to the table and easy to re-position without getting out of alignment; a quick-release tool-free hold-down to secure the stock; an accurate, quick-to-adjust stop for setting precise mortise depths; an adjustable handle that moves the column up and down smoothly; and a chuck that is easy to access when you need to change the bit. Some high end models offer titling heads for cutting angled mortises.