"swasti" also known as swasthika in sanskrit is a sacred symbol of the hindhus.It is often found painted on the wall, door front,etc. in a common Indian home.If it is viewed closley you will realise that it is connected to the 4 cardinal directions.It is believed to protect the house and its peace by blocking it from 4 directions.
Siddhaṃ = "accomplished" or "perfected"
Source ~ Net