LJ6109
"handrail" and "guard rail" defined:
A GUARD and HANDRAIL as defined by code (the '03IRC SECTION R202) :
simply put ...A Guard Rail is a rail that serves as that part of a GUARD. A complete guard additionally employs the use of properly spaced balusters or some other components to inhibit a fall to a lower level from below that guard rail.
A Handrail is a component of a staircase that is used as a tool to assist people during the laborious process of ascending and descending stairways to help maintain their balance while secretly wishing they had purchased an elevator.
A Handrail can also be a Guard Rail if it meets the legal requirements, but in some cases a Guard Rail can't be a Handrail if it's too big to get your hand around, or it's too high to grab on to. The minimum and maximum height of a handrail when used as a guard rail, and the grasping circumference of a hand rail is clearly defined in the code (specifically sections 311.5.6.1 Height, 312.1 Guards required, and 311.5.6.3 Handrail grip size. )
confused yet? I've been doing this for 15 years and I barely understand that difference.
For the sake of simplification.... These rail profile photos below (and about 4000 others) meet the requirements of both types of rail (hand and guard) if installed properly:
LJ6010
LJ6109
LJ6601
LJ6C01& LJ6701
LJ6005
(plowed
rail)
LJ6400
LJ6900
LJ6519
LSP 8000
LSP 6710
LSP9100
OWM8300
OWM1520 
OWM6400
OWM6542
OWM9100
OWM8800
OWM8500
OWM8200
LJ = LJSMITH
LSP = LEEPERS STAIR PRODUCTS
OWM = OLD WORLD MILLWORKS
Rail Fittings are components that match a given profile and allow the rail to make a turn in direction, pass over a newel, or terminate the railing. Fittings are used in every "Over the Post" system and occasionally with "Post to Post" systems depending on the layout. In the event that an uncommon change in direction occurs, a hand carved fitting is shop or site fabricated to meet this need.
The Twist Fitting is hand carved on site in most cases and allows the rail to make a custom compound turn in direction.
Bending Rail is made for most of the above profiles and can be fabricated for any profile.
This type of laminated rail is commonly used on curved stairs and landings.
Plowed Rail is made for the utilization of square top balusters, or to recess a welded iron cap rail. A plow (or plough) is a type of dado joint on the underside of a rail most commonly 1 1/4" or 1 3/4" x 3/16" deep depending on the baluster size. (See the photo of LJ6005 above) Any rail profile can be plowed to fit any baluster or iron cap that measures less than the width of the underside of the rail. The gap or space between balusters in the plow is filled with what is called a Fillet. (pronounced fill-it)
This
is one sample of 1 1/4" fillet.
Shoe Rail is a component that is most widely used to accept the bottom of the balusters elevated above a tread, or on top of a curb wall. This component is also plowed and used in conjunction with fillet. Curb Caps and Shoe Rails
This is one sample of Shoe Rail.