They are to keep the HV caps spaced apart the right amount, and prevent them from rattling into each other from (severe) mechanical shock and vibration. You don't really need them if the unit won't be banged around too much, but since you have them anyway, they should go back in place. I don't recall what retains them - Tek sometimes used a gob of silicone goop, and sometimes a rubber "mouse tail" wrapped around them, that was pulled through holes in the board.
Ed
