Yantra may be used to represent the astronomical position of the planets over a given date and time. It is considered auspicious in Hindu mythology.
These yantras are made up on various objects i.e. Paper, Precious stones, Metal Plates and alloys. It is believed that constantly concentrating pray of God or Devi /Devta helps us to build fortunes, as planets or nominated Devi /Devta have their peculiar gravity which governs basic emotions and karma.
These yantras are often made of Rock Crystal, Copper plate, brass plate, Gold, Silver or Asht metal in shape and composed in pattern of commonly in dots,lines, square, triangle, cirle, floral, representing in different ways the subtle energies.or many other designs with complex and detailed symbols, mantra on a particular date and time according to procedures defined in the vedas. Every Yantra is delimited from the exterior by a line or a group of lines forming its perimeter.

These marginal lines have the function to maintain, contain and prevent the loss of the magical forces represented by the core structure of the yantra, usually the central dot. They also have the function to increase its magical and subtle force.
A yantra is a very complex spiritual instrument in the taantrik practice . It can calm and focus the activities of the mind, and by its positive energy it has a benefic impact on the health and psychic well being of a person.
Yantra function as revelatory conduits of cosmic truths. Yantra, or instrument are work on spiritual technology. Certain yantra are held to embody the energetic signatures For example, the Universe , consciousness , ishta-devata.

Though often rendered in two dimensions through art, yantra are conceived and conceptualised by practitioners as multi-dimensional sacred architecture and in this quality are identical with their correlate the mandala .
Meditation and trance induction that generates the yantra of the subtle body in the complementary modes of the utpatti-krama and sampanna-krama are invested in the various lineages of tantric transmission as exterior and interior sacred architecture that potentiate the accretion and manifestation of siddhi .

Mostly The Yantras are made or Siddha by Panditji or Priest according to their religions. But I think do your work yourself. To maintain power of yantra you must be pray or pooja daily yourself by chanting Mantra according to yantra for five minutes to reap benefits , otherwise the yantra will not work properly.

There are negative energies around us . These negative energy obstacles in our way of achieving greater success, affluence, Harmony and Peace. Many times we find that life is out of our control.
We find ourselves in a position of Extreme stress , lack of peace and harmony , high degree of anxiety , friction in relationship with others , Bad investments , faltering business , stagnation in life and profession , decreasing financial prospects , insecure feeling , repeated failures . Though we involve our best efforts , hard work , intelligence and good intentions.