ISFJs in short:

Quiet, friendly, responsible and conscientious.  Work devotedly to
meet their obligations.  Lend stability to any project or group.
Thorough, painstaking, accurate.  May need time to master technical
subjects, as their interests are usually not technical.  Patient
with detail and routine.  Loyal, considerate, concerned with how
other people feel.

About 6% of the population.

Details about ISFJs:

Six out of every hundred people are ISFJs.  Here the primary is to
be of service and to minister to individual needs.  ISFJs carry a
sense of history, a sense of continuity with past events and
relationships.  Traditions and the conservation of resources are
highly valued.

The least hedonistic of all types, ISFJs believe work is good, play
must be earned.  ISFJs are willing to work long, long hours.  When
they undertake a task, it will be completed if at all humanly
possible.

Adhering to an established way of doing things and doing them well
is valued and respected.  The efficiency and effectiveness of an
established procedure is not often questioned.  Procedures dictated
by handbooks are law.  If others violate or ignore these standard
operating procedures, ISFJs are annoyed and irritated, although
they may not always display this reaction.  Usually, such
irritation is turned inward and may be experienced as fatigue and
muscle tension.

ISFJs are super-dependable and seldom are happy working in
situations where rules are constantly changing.  Their major need
to be of service to others leads them into occupations such as
nursing, teaching, secretarial work, medical practice (especially
general practice), librarian work, and middle-management
administrative jobs.

They relate well to people who need them, for example, the sick,
the ignorant, students, and the "boss."  Much satisfaction comes to
them when they are taking care of the needs of another and they
render the service gently and helpfully.  When the recipient is no
longer in need, the relationship may change its character, the ISFJ
becoming disinterested.

They enjoy assisting the downtrodden and can handle better than
other types servility of others.  If a situation calls for such
behavior on their part, they will show "due respect."

ISFJs have an extraordinary sense of responsibility and an
outstanding talent for executing routines which call for repeated,
sequential procedures; for example, ISFJs make extraordinary
secretaries, highly efficient nurses, and dedicated teachers.
Speculation and theory do not intrigue ISFJs, who would rather
leave the less practical matters to others while remaining
themselves practical and down-to-earth.

ISFJs tend to be devoted and loyal to a boss and tend to identify
personally rather than institutionally.  They expect others,
including the boss, to follow procedures and are distressed and
embarrassed when people do not behave as they are supposed to
behave.

ISFJs often seem to feel personally responsible for seeing to it
that people in an institution or business carry out established
rules and routines.  They often are aware of status given by
titles, environment, offices, and the like and can use this to
advantage.

They are aware of the value of material resources and abhor the
squandering or misuse of these resources.  To save, to put
something aside against an unpredictable future, to prepare for
emergencies - these are important actions.

ISFJs may experience some discomfort when placed in positions of
authority over others and may tend to try to do everything
themselves rather than insist that others do their jobs.  As a
result, ISFJs are frequently overworked.

ISFJs are devoted to mate and family and usually are excellent
homemakers.  The home of an ISFJ is likely to be well kept inside
and out.  Interior and exterior are meticulously maintained and
appointed in the traditional manner.

As a parent, the ISFJ expects children to conform to the rules of
society and has a feeling of personal responsibility to see to it
that these rules are honored.

An ISFJ is apt to find the putting on of airs as offensive and
tends to prefer modest, quiet friends rather than more boisterous
ones.  For the ISFJ, people should behave according to their
position in life, and the ISFJ may be annoyed by others who act
either above or below their social or economic station.

The ISFJ female often displays a flair for making the interior of
the home attractive in a time-honored style, provides attractive,
nourishing meals, and maintains the environment in a neat and
orderly state.  To the ISFJ male and female, the home territory is
important to own and to preserve.

While ISFJs are super-dependable, they may be fascinated by and
attracted to the irresponsible, the lush, the glutton.  Many ISFJs
marry alcoholics and then proceed to conduct a rescue-rejection
game without end, with the rescuing phase taking the guise of an
attempt to reform.  Occasionally an ISFJ mother may reveal a
tendency to find humor in the "waywardness" of a son, while raising
her daughters to respect traditions and to do the Right Thing at
the Right Time - always.

ISFJs are frequently misunderstood and undervalued.  Their
contributions often are taken for granted, and the ISFJ as well is
often taken for granted.  This can cause an ISFJ to harbor feelings
of resentment, and this bottled up emotion can gnaw inwardly,
causing the ISFJ much undeserved suffering.