What can I use instead of potassium nitrate if I don't have any?

There are plenty of cigar box ukulele tutorials that use tin boxes instead of wooden ones. So yes, go ahead and make use of those tins instead!

Try doing it on the carpet or grass instead. Beds are very squishy, so you won't get the right support. You are more likely to fall while doing a bridge...

I am by no means an expert, but this what I have learned. If you want to fix your lawn, it isn't a one and done or one month of...

Call centers may not require specific grade or for you to already have training. If you do have training already, it will probably help.

I don't think you should use a cast iron pan but it could work if you are desperate. I would definitely use a gas stove.

You can use fabric paint or markers but these methods will require a little more effort and care for the design to look good and realistic.

You can put it under your bed, unless you have pets, in which case that may not work.You may also want to put it in some sort of cabinet, or...

The next safest surface would be a room with carpeted flooring. That way if you fall it won't hurt as much. Place pillows around you to soften any falls.