Vibration tests require the application of the vibration along 3 orthogonal axis while the shaker vibrates just in one direction. To achieve this requirement it is possible to rotate the item to be tested and mount it on the shaker in different positions, but this is not always factual.
In fact, many items can’t be rotated because gravity would influence the test and modify the final result. For instance, big and heavy items have fixation points studied to resist to item weight in vertical direction and this direction can’t be changed; also items containing liquids or mobile parts can’t be rotated.
The optimal solution to face this problem is to rotate the shaker in horizontal position and connect a slip table. A slip table is a metal plate as light as possible, guided in horizontal direction by guidance’s opposing the minimum possible friction.