in which they are extend perpendicularly to the rail 12 a detent may be formed on the lower portion 32 to engage a sidewall of the rail 12 in such a manner that when the arms 14 are opened all the way the detent forces them to snap to the perpendicular orientation and stay in that position while the tool 10 is in use the installation of tiles on a roof using tool 10 is now described in conjunction with fig2 typically the roof of a building prior to tiling consists of a wood deck 100 the process of roofing consists of installing several overlapping of tiles on the wood deck 100 in fig2 two courses of tiles 102 and 104 has been installed and secured to the deck 100 by nails 106 before the next course is laid the tool 10 is positioned as shown in the figure with the rail 12 resting on top of course 104 at the upper edge of the exposure the exposure is the portion of tiles of a course that is left exposed to view with the rest of the tiles being covered by the successive courses the arms 14 are perpendicular to the rail 12 and extend past the upper edge of course 104 the arms 12 are secured to the deck 100 by temporary nails 110 the distance d between the rail 12 and the first nail 110 is approximately a full size tile plus 3 4 in the web of the skirt 24 lies flat on top of course 104 with the tool 10 in the position described the tiles of.