A vanilla conveyor, or mikoveyor, is a level design trick that allows a level designer to create a functional voodoo script in vanilla Doom.
A vanilla conveyor functions by placing a voodoo doll on the edge of a ledge overhanging a mikoportal, with a barrel placed such that when a strategically placed crusher is activated, the barrel explodes and slightly damages the voodoo doll, sending it into the mikoportal with a horizontal momentum that persists until the voodoo doll reaches the far end of the mikoportal. By strategically placing linedefs with special line actions in the path of the voodoo doll, a level designer can create ersatz "scripted events".
The only known way to move a voodoo doll is by damaging it, which has the side effect of damaging the player's health and making the player's palette redden momentarily. This can be made less noticeable through careful design, but cannot be eliminated.
The level design trick will not function properly in GZDoom, as the movement code is calculated differently. The primary developer of the source port has stated that vanilla conveyors will never be supported in GZDoom, which limits the trick's usefulness significantly.