what's the black bar in simulink?

What's the black bar and where is it in simulink library? Thx.

Answer 1

[Azzi Abdelmalek]

This is probably a Mux block http://www.mathworks.com/help/simulink/slref/mux.html

[DouHao]

but mux block should be

linked to arrows

[Azzi Abdelmalek]

Do you have access to this model in simulink? or it's just an image you have?