We always become amazed to see a lizard staying or walking on vertical wall, which is not possible for us. The reason is pads that are found on lizard’s feet. These pads are made of wide plates or scales covered by a layer of numerous tiny hooks composed of bent tips of cells. These tiny hooks act as a suction pump that helps lizards stay or walk not only on smooth vertical walls, but also upside down on plaster ceilings.
Due to the shape of the minute hooks, the lizard can easily curls its toes upwards to release the wall when they want to move on. During movement on the vertical walls, the lizard curls and uncurls its toes multiple times that create a suction pressure which helps them stick on the walls.
Source: https://timesofindia.indiatimes.com/How-does-a-lizard-walk/stay-on-vertical-and-horizontal-walls/articleshow/42505365.cms