In order to create a kosher “doorway” the crossbeam must rest on or pass directly over the top of the the doorpost “lechi”. Often it is desirable to use a lightpost or telephone pole as a lechi with a wire as a crossbeam. In many cases the light pole is designed with a tapering main pole capped by a ball shaped finial (pole cap) with a narrow neck. In these cases it is acceptable to tie the string around the narrow neck of the finial. Because the neck is narrower than the top of the actual post, the string is guaranteed to cross directly over the pole top creating a kosher lehi.
Unfortunately in many cases the finial or pole cap is as wide as the supporting pole, or in the case of telephone poles is non existant. In these cases it is necessary to create a secure connecting point on the top of the pole. One of the innovations of the LA Eruv society was the design and crafting of a universal pole top adapter. (the Teichman Adapter). The adapter is an “X’ shaped band of flexible stainless steel with a welded half ring on the top center. The adapter can be laid over the top of any shape pole, and the flexible steel arms molded to the profile of the pole. Secure the adapter with a steel adjustable plumbers strap, and bend the adapter tips up to prevent sliding. Now you have a secure, noninvasive connecting point to create a kosher lehi.
Actual adapter installed on a pole is almost invisible from the ground.