Nexus lock

A nexus lock is a construction designed to temporarily lock together two intersecting Threads of magical energy which make up Onora's Weave. They are employed by mages to stabilize sections of the weave when casting particularly risk-prone magics, and to ensure that magically sent messages sent flow unimpeded.

Construction

Nexus locks come in many different shapes depending on the locale and the employed method of thread stabilization. They require a large footprint of land, but the constructions themselves are rarely bigger than a large house or a tower.
They can be intricately engineered machines of wood and steel, which gently guide the errant Threads into place like a weaver does with their fingers, using the operator's magical energy. Others are solid, monolithic structures of lead or stone, designed to wrest the Threads into place by force, the mage's power acting as a lodestone amplified by the nexus lock.

Uses

The magical stability brought by an operational nexus lock is most often utilized to aid in the creation of powerful magical items, and other rituals which similarly high costs and risk involved.
They can be employed in unraveling a curse that has befallen an individual, and due to circumstances the curse can no longer be broken by conventional means. Such processes are always dangerous, but the risks can be better controlled with a nexus lock.
The magical method of long-range communication called threadsinging relies on the overlapping of Threads, and nexus locks are often employed to ensure that such important messages sent via threadsinging make it where they need to.

Hazards

Locking a Thread for too long runs the risk of attracting dangerous Weave-dwelling creatures to the site of the construction. Such creatures are attracted to powerful magic users, and are known to devour or whisk them away.
A lock needs at least one mage to operate it, and often several are employed at any single moment. The process is very tiring, and an uncontrolled shutdown of the process is known to result in catastrophic failure, known to completely annihilate the nexus lock and and level whatever is surrounding it at the time.
There have been attempts to construct and operate a nexus lock to stabilize three overlapping threads at once. So far, none have succeeded, as the raw magical energy required to control so many threads is beyond the reach of mortals, even with the aid of specially built nexus locks.