Panel connectors are used to join indoor P10 panels together at the vertical joint between each column and each row. The X style connector is used to join the panels on all inner joints, and the T style connector is used to join the outside edges. These panel mounts are not compatible with outdoor style panels or P5 panels.
To calculate the number of T connectors needed, subtract one from the amount of columns and rows in your matrix, then multiply each of those numbers by two, and add them together.
Example: let's say you have a matrix that is 5 panels wide and 6 panels tall. You would have (5 - 1) × 2 + (6 - 1) × 2 = 18 T connectors