What is the difference between 端, 縁 and 先っちょ?

Question

I struggle to visualise the differences between 端, 縁 and 先っちょ after reading many examples and definitions online:

The approximate english translations are very similar:

端: end, tip, point margin (synonyms: 端っこ)

縁: rim, brim, edge brink

先っちょ: end, tip, point (synonyms: 先、先端)

I don't understand the difference between these sentences (some might be incorrect)

1. がけ端 vs. がけの縁 vs. がけの先っちょ

2. ベッドの端 vs. ベッドの縁 vs. ベッドの先っちょ

3. 鉛筆の端 vs. 鉛筆の縁 vs. 鉛筆の先っちょ

Another word I found is 際, but I'm guessing this is rarely used.

Probably a related post:

縁＆端: Are these readings still relevant?

I would like to know the contexts and when it's appropriate to use each word.