The surface of an organism is where sensation (and therefore pleasure), and contact with others takes place. It is only possible to know and love others through the surface. A healthy surface is expression of a solid core made possible by the more or less unobstructed flow of feeling to the surface.
On the one hand, the surface can refer to an opportunity to conceal the core. This can happen by placing a 'mask' or a false covering on the real surface. 'Masks' can fool others at times but they cannot interact with others sincerely. An observer who is more alive can discern the true state of things. A common reason for a deceptive mask is feeling shame about the real surface, but a surface that is fully connected to the core does not engender shame.
The task in regaining feeling and purpose is often one of first dispensing with masks, then secondly bringing life and emotion to the surface. It is not enough for the core to be strong or noble, the surface must reflect the core. But to 'make use' of the surface, it is necessary to have boundaries.
In the 'self-help' culture, boundaries are often described as 1) mental rules of engagement, and 2) defensive stands that prevent exploitation. Having been exploited is believed to be grounds for a label of 'bad boundaries.' There are many maladaptive behavioral strategies that develop around the task of coping with interpersonal risk. One strategy is to avoid contact. Another is to plunge into symbiosis. A third strategy is to analyze other people's behavior for clues of safety and willfully adjust interactional distance. This latter risk-analysis strategy is strongly endorsed culturally, and is generally what is called having boundaries. A big weakness is it tends to fall apart in the face of strong feeling.
Functional boundaries are a biological and energetic thing, however. Bad boundaries are boundaries that are are faint in a biological sense. Most 'neurotic' indirect behavior comes from the state of weak boundaries and the need to protect oneself and further interests some other way. Contact with boundaries of others are meant to be felt. Bringing expression and feeling strongly to the surface provides a natural boundary that has the advantage of being clearer in situations where feeling is strong. Boundaries make both kindness and firmness possible.
Interacting with the boundaries of others involves feeling. Wherever feeling is low or denied, there is a potential problem with boundary transgression. the Creator character and Communicator character have low feeling but also low aggression, so that boundaries are crossed inadvertently, while pursuing a goal or while upset. The Inspirer character has ample aggression so more direct and frequent transgression are expected. A Consolidator character has ample feeling but very conflicted aggression and so may take others boundaries too rigidly and so not achieve intimacy. The rigid group of characters, (except for the passive-feminine who functions more like the consolidator in this respect) have both feeling and aggression, and so push but not cross boundaries. A boundary transgression may not elicit discomfort in a 'target person,' and conversely, mere discomfort at an advance may not represent a boundary transgression.
Boundaries need to be thought of as not merely defensive but something productive and connecting as well. Asking for something difficult, or participating in a strong group without losing one's purpose and principle, is made possible by boundaries. A metaphor can be taken from the animal world: A cat is often noticed to be comfortable sleeping in the middle of a room, even with many people walking nearby. Only if the cat is touched does it respond, perhaps with a claw. The cat is a 'fight' animal. On the other hand, a sheep is a flight animal. It cannot fight so it is always vigilant for the possibility of a predator, even far off. It is almost always moving somewhat skittishly and oriented toward escape routes. To have good boundaries allows one to be comfortable in the 'middle of things.'