This is a base for a stackable pigeon repeller solution. you can print multiple and stack them together.

You need a 1,5-2,0 mm wire for the spikes. Cut double the length and bend it into a U form and insert in the diagonal hole pairs. Make them long as you wish.

The thing works fine for me, although the wire holes got printed too narrow, had to use a drill bit to enlarge them.

It's not perfect, but does the job... I've included a freecad file if you want to contribute and make the design better.