A simplified form of the Wertheim theory of chemical association has been used to address how ellipsoidal particles with three highly localized interaction sites (head, tail, side) polymerize to form aggregates. Aggregation is allowed for heads with tails subject to an energy parameter, epsilon(a), and for heads or tails with the side spot subject to a different energy parameter, epsilon(c). No side-by-side interactions are allowed. As epsilon(c)/epsilon(a)-->0, the aggregate becomes rodlike, whereas as epsilon(c)/epsilon(a)-->infinity, the object becomes a freely rotating chain or a herringbone pattern. When the present theory is applied to self assembly of type I collagen, it is found that each epsilon(c) and epsilon(a) correspond to the anchoring caused by two H bonds.