Sādhanā has two dimensions: practicing and constructing
If we want to build a temple, first we need to understand mathematics and physics by practicing them for a long period of time, which means perfecting ourselves in solving various equations. We also need to know the materials we want to use, their strength, the possibility of processing them, and their accessibility. Further we also need knowledge of the characteristics of the soil to be built upon, whether underground water is present, etc. All this knowledge comes from long-term practice. Only then can we approach building a temple; otherwise it could not only collapse but also endanger lives.
If the śikharin is entitled to build a maṇḍala, it does not mean that from then on he or she does not need to do subordinate practices. At any given constructed level there are always ‘rest-places,’ where to acquire a further level, a thorough practice of some new principles to be worked out separately is needed. Nonetheless, the mere sādhanā with a maṇḍala can provide good insight into what constructing means.
Sādhanā for individuals and groups
Depending on the number of participants, sādhanā can be divided according to whether it is practiced individually or in a group. Some sādhanās can only be practiced alone, some also in a group or kula. Some specific sādhanās intended to be practiced in a group can be practiced individually as well, but such an attitude in some cases may not make sense.
With a group sādhanā we have two possibilities. In the first case, it is an occasional or regular joint practice which is otherwise mainly practiced alone, probably at home. In the second case, some specific sādhanās are practiced which are primarily designated to be held in groups. Most commonly they are recitations of mantras, but also ritual acts and worship. As of ritual acts themselves, they have two dimensions. In the first dimension the main active role belongs only to the teacher, kulācārya or entrusted pūjārī. In the second everybody is inter-connected to the ritual process to some degree, mainly in visualizations and mantra recitations.