Is it safe to re-use drill holes in a wall

One option especially suitable for this scenario (outdoors, often drilling above your head, with the tube bending and vibrating, using handheld drill) is using special drill bits tailored for fast drilling into sheet metal. The market has numerous offers, including Irwin Turbo Max, DeWalt Extreme 2 and Ruko Fast Cut - the idea behind all those is that the drill bit looks similar to a drill bit for wood and the small tip of the drill bit helps the drill bit dive into thin metal.

One important thing is that you should not proceed to drilling the second wall until you retracted the bit from the hole and checked that there's no metal on the tip. Otherwise the following can happen: the drill bit will burst through the first wall and the metal which the tip was facing will remain on the tip and prevent the tip from contacting the second wall.

Beware of the following downsides:

• these are next to impossible to sharpen in your workshop - prepare to either throw them out or grind them into "regular" shape bits once they get dull
• the price is notably higher compared to "regular" bits
• the "metal on the tip" problem described above
• not that easy to find in an average store, so you should shop in advance

The tackless carpet strips installed on masonry surfaces have short evenly-spaced concrete nails on every strip. They are set in position and with a well placed hammer strike the point of the nail penetrates the concrete securing the strip tightly.

Of course in the real world not every nail hit goes as planned. It's a good idea to have a few spares on hand as some tackles will be missing a nail or a bad hammer blow renders the nail useless.

If you can afford the extra time to install the strips with concrete screws (Tap-Cons) then the strips will be anchored better than nails. Use a 5/32 masonry bit for the small Tap-Con screw.

Some suggestions: If you do use screws along with nails 3-4 per strip should be enough. I found that 2 and sometimes 3 layers of tackles in long rooms will not pull loose overtime.