A closure device or door used to cover an opening into a duct, wall, ceiling or enclosure near a fixture that allows access for servicing, such as for the plumbing or electrical system.
access panel (Wikipedia)
A custom online panel or Internet access panel is a group of pre-screened respondents who have expressed a willingness to participate in surveys and/or customer feedback sessions. The custom online panel is also known as a customer advisory panel, proprietary panel or an online research panel. Respondents become "panelists" by completing a profiling questionnaire. The data collected includes demographics, lifestyle characteristics and media habits, which provides a basis for future survey participation.