Spectacle blind/Skillet blind/Spade

Most of the difference is in the "terminology"

1) Some people call it a "Spectacle Blind" and other people call it a "Figure 8 Blind". These have two round segments joined by a strip of metal. One segment is a solid plate and the other is an open ring. These should be restricted in use by weight and handling capabilities.

2 & 3) Both of these are the same. Some people also use the term "Disk". These are all single solid plate segments that block the flow.

4) Along with the "Disk" there is the "Donut" which is the single open ring segment. The separate "Disk" and "Donut" should be used in the larger sizes where the weight of the "Figure 8" becomes too heavy for normal handling.

Check with your local vendor for the terminology used in there catalog.

-normally if you want to isolate permanently,you will use spade blind, because its cheaper(easy to fabricate/ less material) - spectacle blind is unique on purpose, during my days in petroleum refinery, after every shutdowns you have to identify if lines are properly normalized, you can check it by looking which side of the blind is inserted. got what i mean? skillet?new to me