In their hologram state, they are half substance and half light. When the Keepers focus, they are able to become pure light and pass through objects. This process is called going "all clear". Finn has been able to master this ability more than the other Keepers. During this focused state, they are able to hover, but as soon as fear enters their minds, they will fall. While in a bodily state, Finn has even been able to focus enough to go all in to avoid Greg Luowski's punch. After exerting themselves in the form of light, The Keepers exhaust themselves and become tired and sluggish. Also, introduced in Shell Game was version 2.0 which all-clear isn't determined on fear and much easier to go into. It was also easier for them to blend in and look more realistic because the blue line around them was gone so they didn't glow. But in The Insider, they had to return to version 1.6.