Create an empty record

Hi

How would one goabout creating an empty record (for use in relations).

Eg
create table product(
    productid    SERIAL NOT NULL,
    product    TEXT,
    PRIMARY KEY(productid)
);

create table product_billable(
    productid    INT4 NOT NULL,
    billaddress    TEXT,
    PRIMARY KEY (productid),
    FOREIGN KEY (productid) REFERENES product(productid) ON DELETE CASCADE
);

All fields except for the primary key can be NULL.

What if I wanted to add a new billable product but I have not got a name
for it yet?

So how could I insert a new record in product that can be used in
product_billable?

I have tried INSERT INTO product() VALUES(); but as expected it did not
work.

All help appreciated
Best regards
Per-Olof Pettersson