Breed standard with some explanations, 
not strictly according to any specific breed standard, but how it is in real life...


BEHAVIOUR, TEMPERAMENT & PROPORTION

Dignified, intelligent, aloof with strangers, but showing no aggression or shyness.
Stable, fearless, intelligent, reserved with strangers, yet accepting of his master's judgment. In the show ring, a reserved attitude should not be confused with shyness. Unnecessary aggression is not to be tolerated.
A mature Ridgeback should be symmetrical in outline, slightly longer than tall but well balanced.

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HEAD       The head must be in proportion with the rest of the body. The backskull is flat, never domed, free from wrinkles when in repose. When the ears are brought forward in an alert position, the skin is furrowed with expressive wrinkles on the backskull between the ears and above and between the eyes. The planes of the backskull and muzzle are parallel and equal in length. Cheeks are clean and flat, not rounded or bulging. The head should never give a wedge shaped impression.

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SKULL Should be of a fair length (width of head between ears, distance from occiput to stop, stop to end of nose, should be equal), the skull flat and broad between the ears and the head should be free from wrinkles when in repose.
STOP The stop should be reasonably well defined and not in one straight line from the nose to the occipital bone.
NOSE The nose should be black or brown. A black nose should be accompanied by dark eyes, a brown nose by amber eyes.
MUZZLE The muzzle should be long, deep and powerful, finishes up fairly full in width, strong in underjaw.
Depth of muzzle should be in the muzzle itself, not in the leather of the lips alone.
LIPS The lips should be clean, closely fitting the jaws
MOUTH/
BITE
Jaws strong, with a perfect and complete scissor bite, i.e. the upper teeth closely overlapping the lower teeth and set square to the jaws. The teeth must be well developed, especially the canines or holders.
CHEEKS Cheeks should be clean.
EYES Should be moderately well apart, round bright and sparkling, with intelligent expression, their colour harmonising with the colour of the coat.
The eyes should be spaced moderately well apart, rounded, bright and sparkling with intelligent expression, not small, recessed nor sunken. The color should harmonize with the pigmentation of the dog. Black-nosed (pigmented) dogs should have a brown to dark brown eye. Liver or brown-nosed dogs should have an amber-colored eye, with preference given to the darker shades of brown or amber. Yellow eyes on a black-nosed dog are undesirable.
EARS Should be set rather high, of medium size, rather wide at base, and gradually tapering to a rounded point. They should be carried close to the head.
When the ears are brought forward to attention, they are raised even with the top of the head. The ears should hang close to the head and cheek, flaring outward to frame the head.
NECK Should be fairly long, strong and free from throatiness.
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BODY          A Ridgeback represents the perfect balance between power and elegance. The power should come from soundness and conditioning, not from excessive size. The elegance comes from style, presence and carriage. The Ridgeback should give a clean appearance with body lines blending smoothly. A male should be masculine, not coarse or cumbersome. A bitch should be feminine but strong, not weak or delicate.
The Ridgeback is an athletic dog, clean-muscled, upstanding, well balanced and smooth in outline, a dog intended to hold large and dangerous game at bay. He is agile, quick, light on his feet and intelligent enough to stay out of harm's way, brave enough to defend his master.
Overall balance and symmetry is most important.

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BACK/
TOPLINE
Powerful.
The topline flows smoothly from the top of the head down the neck and over the shoulders. The point above the shoulders is the highest point of the backline, never lower than the loin or hindquarters, standing or moving. The back is firm, standing or moving- neither swayed nor roached. The loins are strong. The arch of the loin should not be exaggerated. The croup is neither flat nor steep but blends smoothly and finishes out with the tail set neither too high not too low. 
LOINS Strong, muscular and slightly arched, powerful
CHEST Should not be too wide but very deep and capacious and brisket should reach to the elbow.
FORECHEST Should be visible when viewed from the side.
RIBS Moderately well sprung, never rounded like barrel-hoops.
TAIL Should be strong at the root and gradually tapering towards the end, free from coarseness. It should be of moderate length. It should not be inserted too high nor too low, and should be carried with a slight curve upwards, never curled.
FOREQUARTERS The forelegs should be perfectly straight, strong and well boned, with the elbows close to the body. When viewed from the side, the forelegs should be wider than when viewed from the front. Pasterns should be strong with slight spring.
FORELEGS The bone of the front legs should have plenty of substance, more so when viewed from the side than from the front. The pasterns should be strong and slightly sloping.
SHOULDERS The shoulders should be sloping, clean and muscular, denoting speed.
The shoulder blades should be long, well laid back and sloping: upper arm is of equal length and placed so that the elbow falls directly under the withers.
FEET The feet should be compact and round, with well arched toes, and tough elastic pads, protected by hair between the toes and pads.
The feet should be well knuckled up with thick pads. Flat, thin-padded and splayed feet are incorrect.
HINDQUARTERS In the hind legs the muscles should be clean, well defined, good turn of stifle and strong hocks well let down
The strong, elastic muscles of the hind legs should be carry well into the inner and lower thighs. The stifles are moderately well bent. Hocks should be well let down and straight from hock to pad. Rear angulation should balance and compliment the front. The muscling should be clean and well defined, denoting speed and agility
GAIT/
MOVEMENT
Straight forward, free and active.
The trot should be effortless and flowing, covering the maximum amount of ground with the least amount of effort. As speed increases, the legs angle inward toward a center line beneath the body. The head is carried slightly above the level of the back, the backline remains level and firm, never high in the rear or loin. The tail blends smoothly, carried slightly above the level of the back, never gay nor curled. At all speeds the gait is effortless, rhythmic and smooth, denoting efficiency, presence and style.
COAT Hair should be short and dense, sleek and glossy in appearance, but neither woolly nor silky.
COLOUR Light wheaten to red wheaten. A little white on the chest and toes is permissible, but excessive white hairs here, on belly, or above toes is undesirable. A dark muzzle and ears permissible. Excessive black hairs throughout the coat are highly undesirable.
A Ridgeback hair is banded, lighter at the base, darker at the tip. The color may range from light wheaten (buff) through various shades of gold to red wheaten; all shades are acceptable. Lighter wheaten highlights are usually noted over the shoulder blades.
Clear-faced dogs or dogs with black on the muzzle, ear and around the eyes are equally acceptable. However, these black points should not continue as a solid mask over the eyes. Ridgebacks with black pigmentation may have black hair interspersed throughout the coat; dark brown hair may be seen on a liver/brown-nosed dog. If the amount of black or dark brown is excessive, it is undesirable.
SIZE The desirable heights are:
Dogs  63cm (25ins) to 69cm (27ins)
Bitches  61cm (24ins) to 66cm (26ins)
WEIGHT Desirable weight should be a guideline. Appropriate weight should correspond with the height and bone structure of the dog/bitch. A heavier-boned animal may weigh more, a finer-boned animal less than the 85/70 pound ideal as described in the Standard. Nowadays the rrs seem to be heavier than the standard says.
The desirable weights are:
Dogs 36.5kg (80lbs)
Bitches  32 kg (70lbs)
RIDGE The Standard is very precise regarding the ridge. The ridge is located on the dog's back. Any variation in length of ridge or placement of crowns (whorls) is incorrect and is to be considered a fault. The amount of variation and the severity of the fault is up to the individual assessing the dog. The width of the ridge is immaterial. Occasionally there will be a parting of hair at the top of the ridge. This is not to be considered a fault unless it contains a complete crown (whorl). 
There are many different type of ridges which are acceptable, the basic rule is that it should be long/wide enough with 2 crowns placed in the beginning, parallel. What is a good ridge with some judge, might be a bad with other...
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SOURCE: Breed Standards from RRCUS, RRIF & my own mind