Confusion about using FindControl in pages with master pages

The master page is referenced by the current page, and the control cannot be found with FindControl.

FindControl method searches only the direct or top-level container of a page, and it does not recursively search for the control in the naming container contained in the page.

also FindControl can find Contentup and the Contentdown but I can't find them . Label , Text and the Button .

ContentPlaceHolder Cphup;

Label Lbllabel;

Cphup = (ContentPlaceHolder) master.findcontrol ("ContentPlaceHolder1");

Lbllabel = (Label) cphup.findcontrol ("Lblinfo");

Confusion about using FindControl in pages with master pages