When setting expansion-type anchors, what should be used to ensure the anchor remains flush with the surface?

Using a washer or plate when setting expansion-type anchors is essential for ensuring that the anchor remains flush with the surface. The washer or plate acts as a support that distributes the load evenly and prevents the anchor from sinking deeper into the substrate than intended. This is particularly important for maintaining the integrity of the installation and ensuring that the anchor functions effectively, as expansion-type anchors rely on the friction created against the sides of the hole in the material to secure themselves.

In contrast, other options do not assist in achieving a flush installation. A spacer, while useful in certain contexts, may not provide the necessary support in this scenario. A drill bit is used for creating the hole for the anchor but does not affect the flush finish once the anchor is installed. A hammer could assist in driving the anchor into position, but it does not provide any structural support to keep the anchor flush with the surface. Therefore, the washer or plate is the most suitable choice for achieving a proper installation of expansion-type anchors.