Abstract: An adjustable safety block assembly is disclosed which can be used to traverse an opening for a sliding door in order to block it. The assembly consists of inner and outer tubular members which can be telescoped together. One of the tubular members has a series of axially extending rows of holes spaced at even intervals, and staggered around the radius of the two. The other tubular member has groups of evenly axially spaced circumferentially distributed holes radially arranged. The tubular members may be telescoped until the desired length is achieved, and then holes of the inner and outer tubular members aligned so that locking means can be inserted through the aligned holes to fix the tubular members in relative position, to form a rigid bar. Thus, the safety block is easily adjustable to accommodate any patio door widths, and may be disassembled for storage and travel.