There is no screws to attach cables but plastic pinches. I am confused.

Edited September 6, 201214 yr by Gik

Looks like you wrap the telco wire around the "posts" and pull in and down to make contact.

Never seen one like that before, do you have a part number to google?

Is there a wire strip gauge on the block? strip the wire to that lenth and push wire into block - it will hold the wire. Pressing on the tab or sometimes the hole opens the slot for the wire to release and pull it back out. Try pushing on a tab with small screw driver and see if the hole opens when you do.