29 CFR §101.43

1. (a)A copy of the petition is served on all other parties.
2. (b)Interested persons may request intervention by a written motion to the Board. Such intervention may be granted at the discretion of the Board.
3. (c)All other parties may reply to the petition in writing.
4. (d)Briefs may be filed.
5. (e)After review of the record, the Board issues a declaratory order as to whether it will assert jurisdiction over the cases, but it will not render a decision on the merits at this stage of the cases.
6. (f)The declaratory Board order will be binding on the parties in both cases.