テーブル

How it works

の (of) links テーブル (table) to 下(した) (under), giving "under the table" — Japanese puts the location word (下(した) (under)) after what it relates to. There's no verb "is" here; the place phrase stands alone, with the final よ (you know) added to tell the listener something they didn't realize. So: "It's under the table, you know."