Abstract: The invention relates to a removable tilt-out window construction in which a window may be rotated 90.degree. from its normal vertical position and such rotation causes a slidable block connected to a spring counterbalance to be locked in place to prevent violent release of the spring upon removal of the window. The invention describes a weather strip (30) having a slidable block (68) with a rotatable locking cam (90). Slidable block (68) rides on tracks (64 and 66). Locking Cam (90) can be rotated so that it forces tracks (64 and 66) against the sides of slots (110 and 112) to frictionally engage the slidable block (68) into a fixed position. A window sash (22) is connected to the locking cam (90) to provide rotation thereof to lock slidable block (68). Window 22 may be removed from engagement with locking cam (90) if desired.