In shop floor workbench you can select the operations connected to the block and use Issue Operation Material Manually assumed all operations are connected to at least one common component part. 

The total quantity entered in this dialog will be distributed between the operations according to their required quantity. 

Thanks Björn, working as you describe. Then, how do we unissue the operation material proportional?

There’s no corresponding way of to unissue. You have to do it for each shop order separately. Since unissue is an exceptional transaction it is typically expected to have a less streamlined process there I think.

It is actually something that is in our flow. We do it daily. We are working with sheets that we mill. Like below:

 We issue 1 sheet (pcs) and unissue a part of a sheet.

Thank you for the explanation. 

Thanks @Hans Andersen . Now I understand your process, unfortunately I think you will have to unissue the relevant quantity to each shop order manually. Or of course, if you have the information on how much of the sheet you will need for the block already when you issue it, just issue the part of the sheet that you’re actually going to consume.

if you have the information on how much of the sheet you will need for the block already when you issue it, just issue the part of the sheet that you’re actually going to consume.

For several reason (long explanation), not possible.