fig1 shows a prior art interface or probe plate 1 , which contains a first face 6 , and a plurality of holes 4 . the holes 4 are drawn in a rectangular array , but it will be appreciated that the holes 4 may be configured arbitrarily on the plate 1 . as used in a circuit board tester , the plate 1 is typically built into the tester , and typically provides a mechanical surface against which parts may be held during the test procedure . a fixture that contains a circuit board under test may be placed rigidly in contact opposite the grooves 3 on the second face ( not identified in fig1 ) of the plate 1 , and a plurality of electrical probes access various points on the circuit board through various holes 4 in the plate 1 . during the testing procedure , the probes apply and measure various voltages and currents at specific locations in a circuit board under test , generally to ensure that the circuit performs adequately . typically , a single probe corresponds to a single hole 4 in the plate 1 . prior to usage of the tester , the various electrical probes must be configured to test specific locations in a particular circuit . the probe locations are typically generated at the cad ( computer assisted drafting ) level , usually by the same tools that lay out the components on the circuit boards . the probe locations may be documented in cad drawings and communicated to a technician that configures the probes manually , or may be encoded and communicated electronically to an automated device that configures the probes . once the tester probes are properly configured and the plate 1 is attached to the tester , a subset 4 a - 4 h of the holes 4 in the plate 1 will receive probes during operation of the tester . the remainder of the holes 4 that are not in the subset 4 a - 4 h do not receive probes during operation of the tester . it will be appreciated that the number and locations of the holes in subset 4 a - 4 h depend on the circuit under test , and are relatively unimportant for the present invention . the final step in the manufacturing process for the prior art plate 1 is a manual identification of the subset 4 a - 4 h of holes 4 that receive probes . the manufacturer of the prior art plate 1 then manually marks each hole 4 in the subset 4 a - 4 h by hand , typically by painting ( i . e . using an indicator ( indicia )) a small area around each hole 4 in the subset 4 a - 4 h on the first face 6 . thus , it is the painted areas which are to have probes inserted . although the marked areas surrounding each hole 4 in the subset 4 a - 4 h are drawn as circular in fig1 , it will be appreciated that the markings may be of any shape or pattern , as long as each marking is readily identifiable with exactly one hole 4 in the subset 4 a - 4 h . they do not have concentric paint markings . the indication or indicator marking can be adjacent the hole , so long as it is clear which hole is referred to . a severe drawback to the manual marking system of the prior art plate 1 is that it is very labor - intensive , and therefore very expensive . for a plate 1 that requires dozens of markings , in an array with hundreds of holes , the marking procedure can be quite significant , and in some cases , can be the greatest expense in producing the plates 1 . although one may be tempted to fabricate a new plate for each circuit under test , with holes only where probes are placed , this would be expensive and largely impractical . the prior art plate 1 is generally molded from a plastic material , such as polycarbonate , and has its holes incorporated into the mold itself . a custom prior art plate 1 molded in this manner , with holes only where required by the user , would require a custom mold for each user , which is impractically expensive . additionally , the drilling of holes in a blank plate , while possible , is also more expensive than the prior art technique of manually marking the holes . accordingly , there is a need for a plate that has a large number of holes for flexibility , but has a way of inexpensively identifying a subset of the holes to simplify the final inspection of the tester . fig2 shows a plate 11 in an embodiment of the present invention . a coating 15 is applied to a first face 16 of an uncoated plate 12 , preferably in the area ( grooves ) between the ridges 13 . the outwardly extending ridges 13 may be coated as well , but at the risk of flaking or peeling of the coating 15 . the uncoated plate 12 contains a plurality of holes 14 , and the coating 15 does not fill in the holes 14 . the coating 15 may be a paint , a two - part epoxy , or an other opaque coating , preferably of a color of a high contrast with the color of the uncoated plate 12 . preferably , the coating 15 is not electrically conductive . for example , if the uncoated plate 12 is dark - colored , a suitable coating 15 may be commercially available ; “ polane t - white ” paint . the paint 5 is preferably in high contrast to the unpainted color of the bare plate 2 . for example , if the bare plate 2 is a dark - colored polycarbonate material , then the paint or ink 5 should be a light color ( any contrasting color will do ), so that the marked holes 4 are readily visibly detected , by eye or by a machine vision system . in the case where a drilling machine will remove the paint , which is the preferred solution , we have found that it is important to match the paint with the base material very carefully . in initial attempts , we found that the drill would not only scrape a circular hole , but also cause the paint to chip and remove paint from adjacent holes . vibration might also cause the paint to flake . the preferred base material is a hard plastic , so a paint which adheres well ( such as that mentioned above ) should be chosen and tested . thus in our preferred solution , the indicator , or paint applied to the base plate should fixedly adhere thereto , so that when being drilled , scraped or otherwise removed to as the hole marker . in a subset 14 a - 14 h of holes 14 , the coating 15 has been removed in the region around each hole 14 in the subset 14 a - 14 h , exposing the first face 16 underneath . because the coating 15 contrasts with the color of the uncoated plate 12 , each hole 14 in the subset 14 a - 14 h is readily visually identifiable , whether by eye or by a camera in a machine vision system . preferably , the removal of the coating around each hole 14 in the subset 14 a - 14 h is performed by an automated tool , such as an automated drill that receives a set of subset 14 - 14 h locations from a cad file . the automated drill preferably uses a drill bit larger than the hole 14 diameter , and drills only enough material to completely remove the coating 15 , without substantially drilling through the first face 16 . for example , if the coating 15 has a thickness of roughly 0 . 1 mm , then the drill may remove roughly 0 . 5 mm of material . the uncoated plate 12 may be substantially thicker than 0 . 5 mm . note that drilling such shallow holes is an inexpensive procedure compared to drilling comparable through holes , and that very little waste material is produced . additionally , if the user decides to add another hole 14 to the subset 14 a - 14 h , he may mark the added hole by hand , simply by turning a drill bit centered in the hole by hand and grinding for a few seconds ; the coating 15 comes off readily . it will be understood that the grooves 13 on the plate 11 are not essential for the present invention . a similar coating 15 may be applied to an uncoated plate that has physical features other than grooves , such as posts , or has no physical features at all . the coating 15 may be applied to the regions between holes 14 , so that when removed , the hole may be readily visibly identified by eye or by a machine vision system as part of the subset 14 a - 14 f . as used in a circuit board tester , the plate 11 of fig2 would readily identify the subset 14 a - 14 h of holes 14 that receive probes during operation . because of the high contrast between the coating 15 and the color of the uncoated plate 12 , the technician easily sees the exposed first face 16 in the regions around each hole 14 in the subset 14 a - 14 h , and can then quickly complete the final inspection of the probe locations prior to operation . if the technician finds any holes 14 in the subset 14 a - 1 4 h that are missing a probe , or finds a probe in a hole 14 that is not in the subset 14 a - 14 h , he can take corrective actions . because the entire subset 14 a - 1 4 h is visible all at once to the technician , without the need for manually counting rows and columns , the efficiency of the inspection process is greatly improved . typically , when a tester is customized to test a particular circuit , a set of drawings is made by a computer assisted drawing ( cad ) machine , well known in the art , and presented to a technician . the technician uses the drawings to configure the tester , and the drawings typically indicate the locations and types of the probes . alternatively , the cad machine may generate an automated set of instructions for placement of the probes during assembly of the tester . in the present invention , the cad machine may generate an additional set of instructions for denoting which holes in the plate are to receive probes . the additional instructions may be used by an automated drilling machine that ablates or scrapes off the paint in the area surrounding each hole that receives a probe . the drilling machine uses a drill bit of a larger diameter than the hole , and only drills until the paint is removed ; it does not drill substantially into the plate itself and does not increase the diameter of the hole . once the paint is removed around a particular hole , the hole is readily identified visually , either by eye or by use of a machine vision system . “ visual ” in this context there is not limited to vision related detection . it includes optical and non optical methods . it can also include machine - readable detection / recognition , tactile detection , by creating ridges , depressions , etc . once the tester is configured , each hole in the subset should contain a probe , and no probes should be present in holes not contained in the subset . once all the probes are configured , a final visual inspection of the tester is relatively simple , as the technician may simply look at the plate and ensure that each hole in the subset has a probe that extends through it , and that none of the probes extend through holes not in the subset .