wind clips

[jjcold]

I've noticed most builders (of course, not mine!) use these clips between sheets of roof sheathing, in the middle of the truss bays. What is the purpose of those clips? Do they do anything to prevent sagging between bays that I've noticed on some older roofs?

[Rich]

That's exactly what they do - help support the sheathing seams between sheets. Essentially it helps the compound span of the sheathing of one piece to hold up the other sheet...etc..etc. By compound span I mean it spans over several rafters - weight from one bay lifts the adjacent bays and vice versa.
Typically they are only used on 1/2" but it's not a bad idea to use them with 5/8" also.

[grumpydasmurf]

They also space the sheets. You need 1/8" spaceing between sheets for expansion purposes.