Exact assessment of subjective deviations requires laboratory facilities but a plain wastepaper basket may be adapted to suit basic clinical needs. The simplest way is to attach two parallel pieces of sticky tape of a contrasting color diametrically across the bottom of the basket, one on the inside and one on the outside. The subject's task is to grab the basket with both hands and stick his or her face into the basket's opening. Then, the subject should turn the basket along its longitudinal axis until the inside tape strip appears to be exactly vertical. The examiner judges the position by looking at the tape strip on the basket's outside. A plumb line or a protractor can be added if quantitative measurements are desired. This is actually a funny test. The examiner has to be prepared to endure ridicule from patients and bystanders on first sight of the test device but their attention to the test results will be unparallelled .
An alternative arrangement is to use the enclosed screen-based protractor. To exclude all environmental cues (including the screen's frame), the screen should be viewed through a cardboard tube or a wastepaper basket with its bottom cut away. To change the protractor's angle, drag the mouse left or right. The current angle relative to the screen vertical is indicated in the upper left corner.