On the skateboard, the Yud manifests as the nuts on the bolts, the strong points of adhesion which, though small, hold most components of the skateboard tightly together.
Dots are signified by the letter Yud, י. Yud is the building block of all the other letters, for a scribe begins writing all letters with a Yud and then extends it to form specific letters. The shape of the Yud signifies strong contraction and concentration. The word Yud connotes a hand - a Yad - which is capable of contracting and holding something firmly. Yud is the adhesive element in reality.
Psychologically, the dot signifies the ability to maintain focus on a goal, the ability to hold thoughts within one's awareness for as long as is necessary. Without this ability, one's energy tends to dissipate and one meanders aimlessly through life.
The square signifies a platform or a contained area such a room or box. It is related to the letter Heh, ה. Grammatically, Heh is used to signify a definite article - 'the' - where one refers to a specific and clearly defined object. Compare: 'do you like apples' with 'do you like the apples'. The latter has a clearer boundary.
Psychologically, it's important to have clear boundaries and rules to live by. These provide the consciousness with stability and allow one to monitor where he's headed and how he's progressing. Without clear cut rules one is forever insecure or unmotivated to make a move. On the other hand, one must be capable of thinking out of the box - to break the box open - when necessary or appropriate. Hence the letter Heh is one of only two Hebrew letters which are broken into two components. One must have boundaries but not be trapped by them.
The wooden deck, the platform on which the skater comfortably stands relates to the square and the Heh. (The curvature at the front and back ends of a board, which are associated with the circle, offer leverage for the performance of tricks and for directing the board. The basic board, however, is rectangular.)
Lines are related to the letter Vav, ו, which means a 'hook'. Grammatically the Vav's function is conjunction, ('and'), which connects - or 'hooks' - two concepts together.
Psychologically, the line signifies a direct approach, for the shortest distance between two points is a straight line. It is about being simple, honest and straightforward. The key ingredients for a healthy and genuine relationship between people.
The 'hangers' of skateboard trucks (the axles) are two lines running horizontally across the board, connecting the wheels on both sides. Bolts are lines running vertically through the board linking the wooden deck with the trucks.
The circle is related to the letter Samech, ,ס which means support. Circles are often in need of support as they are prone to roll away. On the other hand, circles are often used to provide support: a belt holds up a pair of pants by surrounding the hips, helmets surround the head, elastic bands keep clumps of hair together, a hug is often expressive of emotional support, etc.
Spiritually, the circle signifies the ability to move and shift in one's manner, thinking, life goals, etc. Though movement is a sin qua non for progress, it must be guided to ensure that one travels in the right direction. Without control, who knows where one might end up.
The wheels at the bottom of a skateboard hold up the entire board. Yet, at the same time, they are in need of constant control since they allow the board to roll away.
The above four letters and their corresponding shapes parallel the four letters of the ineffable name of G-d.