The specimen holder has one or two wells at the end. The sample is loaded into this via a flange or a ring that screws into the well to hold it securely in place. It is imperative that the grid is secured so that it does not fall out of the specimen holder.
The holder is then inserted into the column. During this process the sample airlock is evacuated which can take a few minutes. It is important to keep the O-ring on the holder free from lint or dust and properly greased or it can interfere with the vacuum. To keep it clean, the holder is stored in a covering sleeve when outside of the machine. A cable can be observed on some specimen holders. The cable is plugged into the column to enable electronically-controlled tilting of the holder and therefore the sample. This is important for obtaining precisely oriented diffraction patterns and high resolution images.