represent the angle between the projected tangent line 317 and the projected tangent line 315 it may also comprise a third portion comprising a liner receptor slot for receiving a pool liner wherein said third portion comprises a non curved portion therein and wherein a tangential projection off of a first end of said third portion intersects said tangent line of said first portion at a first acute angle for example as observed in fig4 the projected tangent line 317 may intersect with the projected tangent line 318 a of the liner receptor slot of the third portion 318 to form angle u03b8 additionally a tangential projection off of a second end of said third portion intersects said tangent line of said second portion at a second acute angle for example as observed in fig4 the projected tangent line 315 may intersect with the projected tangent line 318 a of the liner receptor slot of the third portion 318 to form angle u03bb furthermore the third portion may comprise an angle corresponding to an acute angle therein forming a concaved form another embodiment may be a corner piece having a third portion that comprises a plurality of angles corresponding to a plurality of acute angles.