Crossarms. 5 type crossarms exist, with 4 pins and with 2 above pins and 2 under J pins (because of the J was cheaper, it is very common), and crossarm for carrier frequency.
It has 4 pins, 2 pins pair. The 8 pins crossarm was used only on double poles (2 pics 4 pins crosarm in one). The pins are welded or screwed. The crossarms are from U-profile steel.
They were used in point-to-point network.
(From MPSZ 111.63-72 Newscast network's steel fittings norm)