Named after Chicagoan J. E. Parker, it is a 3 1⁄2 7 inch box drawn on a balkline table from the termination of a balkline with the cushion , thus defining a restricted space in which only a set number of points may be scored before one ball must be driven from the area. Now supplanted by anchor spaces, it was developed to curtail the effectiveness of the anchor nurse , which in turn had been invented to exploit a loophole in balkline rules: so long as both object balls straddled a balkline , there was no restriction on counts, as each ball lay in a separate balk space.