While locking coax terminator tools are obviously available to be bought, note that using such a tool for accessing cable company-owned enclosures--particularly with the intention of pirating service--is illegal and discussion of such is prohibited in the forums.
Note that while you may not subscribe to any cable services, cable signal is almost always active within this enclosure. The obvious risk here is that OTA signal and cable signals within the same box could be accidentally combined, causing serious issues, such as cable signal "leakage" into the air. The opposite also occurs: OTA signal ingress into the cable plant. Cable companies are legally required to monitor for signal leakage from their plant and fix it without delay.
However, assuming that you somehow own the enclosure, and the locking terminator belongs to you, and there is no active cable line, then this is the procedure for using the tool:
When you pull back the handle, two flanges at the end should retract. At this point you insert the tool end into the locking terminator. You then release the handle, which deploys the tool flanges inside of the terminator. You should now be able to rotate and unlock the terminator.
If the tool cannot rotate easily when inserted into the terminator (with flanges deployed), do not force it. You will damage the tool. The terminator is likely frozen or otherwise seized. Try spraying WD40 into the terminator, or safely warming the box and try again.
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